Anti-gitr antibodies and uses thereof

ABSTRACT

Provided herein are antibodies, and antigen-binding fragments thereof that specifically bind glucocorticoid-induced tumor necrosis factor receptor (GITR) and methods of using the same, including, e.g., methods of treatment using the same.

FIELD

The present invention relates to antibodies and antigen-bindingfragments thereof that specifically bind glucocorticoid-induced tumornecrosis factor receptor (GITR) and methods of use thereof.

BACKGROUND

Glucocorticoid-induced tumor necrosis factor receptor (GITR) is a memberof the tumor necrosis factor receptor superfamily (TNFRSF). GITRexpression is constitutively high on regulatory T cells,low/intermediate on naïve T cells, NK cells and granulocytes, andinducible upon activation. GITR interacts with its ligand GITRL, whichis mainly expressed on antigen-presenting cells. GITR receptoractivation can both augment effector T-cell proliferation and functionas well as attenuate the suppression induced by regulatory T cells.Consequently, the modulation of GITR activity can serve as a basis forcancer immunotherapy and immune disorders. Thus, there is a need foragents, e.g., antibodies that modulate the activity of GITR.

BRIEF SUMMARY

The present invention provides antibodies and antigen-binding fragmentsthereof that bind glucocorticoid-induced tumor necrosis factor receptor(GITR). The antibodies of the invention are useful, inter alia, fortargeting immune cells, e.g., effector T-cells, regulatory T-cells, andNK cells that express GITR.

The antibodies of the invention can be full-length (for example, an IgG1or IgG4 antibody) or may comprise only an antigen-binding portion (forexample, a Fab, F(ab′)₂ or scFv fragment), and may be modified to affectfunctionality, e.g., to eliminate residual effector functions (Reddy etal., 2000, J. Immunol. 164:1925-1933).

Exemplary anti-GITR antibodies of the present invention are listed inTables 1 and 2 herein. Table 1 sets forth the amino acid sequenceidentifiers of the heavy chain variable regions (HCVRs), light chainvariable regions (LCVRs), heavy chain complementarity determiningregions (HCDR1, HCDR2 and HCDR3), and light chain complementaritydetermining regions (LCDR1, LCDR2 and LCDR3) of the exemplary anti-GITRantibodies. Table 2 sets forth the nucleic acid sequence identifiers ofthe HCVRs, LCVRs, HCDR1, HCDR2 HCDR3, LCDR1, LCDR2 and LCDR3 of theexemplary anti-GITR antibodies.

The present invention provides antibodies or antigen-binding fragmentsthereof that specifically bind GITR, comprising an HCVR comprising anamino acid sequence selected from any of the HCVR amino acid sequenceslisted in Table 1, or a substantially similar sequence thereof having atleast 90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising an LCVRcomprising an amino acid sequence selected from any of the LCVR aminoacid sequences listed in Table 1, or a substantially similar sequencethereof having at least 90%, at least 95%, at least 98% or at least 99%sequence identity thereto.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising an HCVR and anLCVR amino acid sequence pair (HCVR/LCVR) comprising any of the HCVRamino acid sequences listed in Table 1 paired with any of the LCVR aminoacid sequences listed in Table 1. According to certain embodiments, thepresent invention provides antibodies, or antigen-binding fragmentsthereof, comprising an HCVR/LCVR amino acid sequence pair containedwithin any of the exemplary anti-GITR antibodies listed in Table 1. Incertain embodiments, the HCVR/LCVR amino acid sequence pair is selectedfrom the group consisting of: 98/106; 162/170; 194/202; 242/250;290/298; 338/402; and 346/402.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising a heavy chainCDR1 (HCDR1) comprising an amino acid sequence selected from any of theHCDR1 amino acid sequences listed in Table 1 or a substantially similarsequence thereof having at least 90%, at least 95%, at least 98% or atleast 99% sequence identity.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising a heavy chainCDR2 (HCDR2) comprising an amino acid sequence selected from any of theHCDR2 amino acid sequences listed in Table 1 or a substantially similarsequence thereof having at least 90%, at least 95%, at least 98% or atleast 99% sequence identity.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising a heavy chainCDR3 (HCDR3) comprising an amino acid sequence selected from any of theHCDR3 amino acid sequences listed in Table 1 or a substantially similarsequence thereof having at least 90%, at least 95%, at least 98% or atleast 99% sequence identity.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising a light chainCDR1 (LCDR1) comprising an amino acid sequence selected from any of theLCDR1 amino acid sequences listed in Table 1 or a substantially similarsequence thereof having at least 90%, at least 95%, at least 98% or atleast 99% sequence identity.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising a light chainCDR2 (LCDR2) comprising an amino acid sequence selected from any of theLCDR2 amino acid sequences listed in Table 1 or a substantially similarsequence thereof having at least 90%, at least 95%, at least 98% or atleast 99% sequence identity.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising a light chainCDR3 (LCDR3) comprising an amino acid sequence selected from any of theLCDR3 amino acid sequences listed in Table 1 or a substantially similarsequence thereof having at least 90%, at least 95%, at least 98% or atleast 99% sequence identity.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising an HCDR3 andan LCDR3 amino acid sequence pair (HCDR3/LCDR3) comprising any of theHCDR3 amino acid sequences listed in Table 1 paired with any of theLCDR3 amino acid sequences listed in Table 1. According to certainembodiments, the present invention provides antibodies, orantigen-binding fragments thereof, comprising an HCDR3/LCDR3 amino acidsequence pair contained within any of the exemplary anti-GITR antibodieslisted in Table 1. In certain embodiments, the HCDR3/LCDR3 amino acidsequence pair is selected from the group consisting of: 104/112;168/176; 200/208; 248/256; 296/304; 344/408; and 352/408.

The present invention also provides antibodies or antigen-bindingfragments thereof that specifically bind GITR, comprising a set of sixCDRs (i.e., HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3) contained within any ofthe exemplary anti-GITR antibodies listed in Table 1. In certainembodiments, the HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3 amino acidsequences set is selected from the group consisting of:100-102-104-108-110-112; 164-166-168-172-174-176;196-198-200-204-206-208; 244-246-248-252-254-256;292-294-296-300-302-304; 340-342-344-404-406-408; and348-350-352-404-406-408.

In a related embodiment, the present invention provides antibodies, orantigen-binding fragments thereof that specifically bind GITR,comprising a set of six CDRs (i.e., HCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3)contained within an HCVR/LCVR amino acid sequence pair as defined by anyof the exemplary anti-GITR antibodies listed in Table 1. For example,the present invention includes antibodies or antigen-binding fragmentsthereof that specifically bind GITR, comprising theHCDR1-HCDR2-HCDR3-LCDR1-LCDR2-LCDR3 amino acid sequences set containedwithin an HCVR/LCVR amino acid sequence pair selected from the groupconsisting of: 98/106; 162/170; 194/202; 242/250; 290/298; 338/402; and346/102. Methods and techniques for identifying CDRs within HCVR andLCVR amino acid sequences are well known in the art and can be used toidentify CDRs within the specified HCVR and/or LCVR amino acid sequencesdisclosed herein. Exemplary conventions that can be used to identify theboundaries of CDRs include, e.g., the Kabat definition, the Chothiadefinition, and the AbM definition. In general terms, the Kabatdefinition is based on sequence variability, the Chothia definition isbased on the location of the structural loop regions, and the AbMdefinition is a compromise between the Kabat and Chothia approaches.See, e.g., Kabat, “Sequences of Proteins of Immunological Interest,”National Institutes of Health, Bethesda, Md. (1991); Al-Lazikani et al.,J. Mol. Biol. 273:927-948 (1997); and Martin et al., Proc. Natl. Acad.Sci. USA 86:9268-9272 (1989). Public databases are also available foridentifying CDR sequences within an antibody.

The present invention also provides nucleic acid molecules encodinganti-GITR antibodies or portions thereof. For example, the presentinvention provides nucleic acid molecules encoding any of the HCVR aminoacid sequences listed in Table 1; in certain embodiments the nucleicacid molecule comprises a polynucleotide sequence selected from any ofthe HCVR nucleic acid sequences listed in Table 2, or a substantiallysimilar sequence thereof having at least 90%, at least 95%, at least 98%or at least 99% sequence identity thereto.

The present invention also provides nucleic acid molecules encoding anyof the LCVR amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCVR nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the HCDR1 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the HCDR1 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the HCDR2 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the HCDR2 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the HCDR3 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the HCDR3 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the LCDR1 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCDR1 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the LCDR2 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCDR2 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anyof the LCDR3 amino acid sequences listed in Table 1; in certainembodiments the nucleic acid molecule comprises a polynucleotidesequence selected from any of the LCDR3 nucleic acid sequences listed inTable 2, or a substantially similar sequence thereof having at least90%, at least 95%, at least 98% or at least 99% sequence identitythereto.

The present invention also provides nucleic acid molecules encoding anHCVR, wherein the HCVR comprises a set of three CDRs (i.e.,HCDR1-HCDR2-HCDR3), wherein the HCDR1-HCDR2-HCDR3 amino acid sequenceset is as defined by any of the exemplary anti-GITR antibodies listed inTable 1.

The present invention also provides nucleic acid molecules encoding anLCVR, wherein the LCVR comprises a set of three CDRs (i.e.,LCDR1-LCDR2-LCDR3), wherein the LCDR1-LCDR2-LCDR3 amino acid sequenceset is as defined by any of the exemplary anti-GITR antibodies listed inTable 1.

The present invention also provides nucleic acid molecules encoding bothan HCVR and an LCVR, wherein the HCVR comprises an amino acid sequenceof any of the HCVR amino acid sequences listed in Table 1, and whereinthe LCVR comprises an amino acid sequence of any of the LCVR amino acidsequences listed in Table 1. In certain embodiments, the nucleic acidmolecule comprises a polynucleotide sequence selected from any of theHCVR nucleic acid sequences listed in Table 2, or a substantiallysimilar sequence thereof having at least 90%, at least 95%, at least 98%or at least 99% sequence identity thereto, and a polynucleotide sequenceselected from any of the LCVR nucleic acid sequences listed in Table 2,or a substantially similar sequence thereof having at least 90%, atleast 95%, at least 98% or at least 99% sequence identity thereto. Incertain embodiments according to this aspect of the invention, thenucleic acid molecule encodes an HCVR and LCVR, wherein the HCVR andLCVR are both derived from the same anti-GITR antibody listed in Table1.

The present invention also provides recombinant expression vectorscapable of expressing a polypeptide comprising a heavy or light chainvariable region of an anti-GITR antibody. For example, the presentinvention includes recombinant expression vectors comprising any of thenucleic acid molecules mentioned above, i.e., nucleic acid moleculesencoding any of the HCVR, LCVR, and/or CDR sequences as set forth inTable 1. Also included within the scope of the present invention arehost cells into which such vectors have been introduced, as well asmethods of producing the antibodies or portions thereof by culturing thehost cells under conditions permitting production of the antibodies orantibody fragments, and recovering the antibodies and antibody fragmentsso produced.

The present invention includes anti-GITR antibodies having a modifiedglycosylation pattern. In some embodiments, modification to removeundesirable glycosylation sites may be useful, or an antibody lacking afucose moiety present on the oligosaccharide chain, for example, toincrease antibody dependent cellular cytotoxicity (ADCC) function (seeShield et al. (2002) JBC 277:26733). In other applications, modificationof galactosylation can be made in order to modify complement dependentcytotoxicity (CDC).

In another aspect, the invention provides a pharmaceutical compositioncomprising a recombinant human antibody or fragment thereof whichspecifically binds GITR and a pharmaceutically acceptable carrier. In arelated aspect, the invention features a composition which is acombination of an anti-GITR antibody and a second therapeutic agent. Inone embodiment, the second therapeutic agent is any agent that isadvantageously combined with an anti-GITR antibody. The presentinvention also provides antibody-drug conjugates (ADCs) comprising ananti-GITR antibody conjugated to a cytotoxic agent. Exemplarycombination therapies, co-formulations, and ADCs involving the anti-GITRantibodies of the present invention are disclosed elsewhere herein.

In yet another aspect, the invention provides therapeutic methods forkilling tumor cells or for inhibiting or attenuating tumor cell growth,or otherwise treating a patient afflicted with cancer, using ananti-GITR antibody or antigen-binding portion of an antibody of theinvention. The therapeutic methods according to this aspect of theinvention comprise administering a therapeutically effective amount of apharmaceutical composition comprising an antibody or antigen-bindingfragment of an antibody of the invention to a subject in need thereof.The disorder treated is any disease or condition which is improved,ameliorated, inhibited or prevented by targeting GITR and/or byincreasing T-cell proliferation or function and/or inhibitingsuppression activity induced by regulatory T cells.

In yet another aspect, the invention provides therapeutic methods forkilling tumor cells or for inhibiting or attenuating tumor cell growth,or otherwise treating a patient afflicted with cancer, using acombination of an anti-GITR antibody or antigen-binding portion of ananti-GITR antibody and an anti-PD1 antibody or antigen-binding portionof an anti-PD1 antibody. The therapeutic methods according to thisaspect of the invention comprise administering a therapeuticallyeffective amount of a pharmaceutical composition comprising acombination of an anti-GITR and anti-PD1 antibody or antigen-bindingfragment composition to a subject in need thereof. The disorder treatedis any disease or condition which is improved, ameliorated, inhibited orprevented by targeting both GITR and PD1.

Other embodiments will become apparent from a review of the ensuingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts average tumor volumes for each treatment group (mm³±SEM)plotted against days after tumor challenge as described in Example 7.Mice were treated with either isotype antibody (open circles, ∘),anti-PD-1 antibody (open squares, □), anti-GITR antibody (open pyramids,Δ), or a combination of anti-PD-1 and anti-GITR (closed invertedpyramids, ▾).

FIG. 2 depicts survival analysis of MC38 bearing mice treated with thecombination of an anti-mouse GITR and anti-mouse-PD1 antibody asdescribed in Example 7. Mice were treated with either isotype antibody(open circles, ∘), anti-PD-1 antibody (open squares, □), anti-GITRantibody (open pyramids, Δ), or a combination of anti-PD-1 and anti-GITR(open inverted pyramids, ∇).

FIG. 3 depicts the individual tumor growth curve of tumor-free or naïvecontrol mice challenged with MC38 or B16.F10.9 tumor cells as describedin Example 7.

FIG. 4 depicts average tumor volumes for mice treated with differentdepletion antibodies as described in Example 7.

FIG. 5 depicts FACS analysis result of intratumoral CD8/Treg, CD4Teff/Treg ratio as described in Example 7.

FIG. 6 depicts percentage and cell number/mm³ tumor of T cell subsets intumor as described in Example 7.

FIG. 7 depicts average tumor volumes for each treatment group (mm³±SEM)plotted against days after tumor challenge as depicted in Example 7.

FIG. 8 depicts survival analysis of MC38 bearing GITR/GIRL humanizedmice treated with the combination of an anti-human GITR- and anti-mousePD1-antibody as described in Example 7.

FIG. 9 depicts FACS analysis of intratumoral and spleen percentage ofCD8 T cells, percentage of Treg cells, and CD8/Treg ratio as describedin Example 7.

FIG. 10 depicts average tumor volumes for each treatment group (mm³±SEM)plotted against days after tumor challenge as described in Example 7.

FIG. 11 depicts survival analysis of MC38 bearing PD1/PDL1 humanizedmice treated with the combination of an anti-mouse GITR- and anti-humanPD1-antibody as described in Example 7.

FIG. 12 depicts a tumor growth curve of MC38-bearing mice as describedin Example 7. The Y-axis depicts tumor volume in cubic millimeters andthe X-axis depicts time in days post tumor challenge. Open symbols (□,∘) represent mice first treated with an isotype antibody (control).Filled symbols (▪, ●) represent mice first treated with an anti-CD226antibody. Those mice then treated with the isotype antibody arerepresented by circles (∘, ●) and solid lines. Those mice then treatedwith the anti-GITR and anti-PD-1 combination are represented by squares(□, ▪) and dotted lines.

FIG. 13 depicts a survival curve of MC38-bearing mice as described inExample 7. The Y-axis depicts percent survival and the X-axis depictstime in days post tumor challenge. Open symbols (□, ∘) represent micefirst treated with an isotype antibody (control). Filled symbols (▪, ●)represent mice first treated with an anti-CD226 antibody. Those micethen treated with the isotype antibody are represented by circles (∘, ●)and solid lines. Those mice then treated with the anti-GITR andanti-PD-1 combination are represented by squares (□, ▪) and dottedlines.

FIG. 14 depicts a tumor growth curve of MC38-bearing wild type mice(represented by diamonds [⋄♦]) or TIGIT knock-out mice (represented bytriangles [Δ▴]) treated with isotype IgGs as described in Example 7. TheY-axis depicts tumor volume in cubic millimeters and the X-axis depictstime in days post tumor challenge. Open symbols and dotted linesrepresent mice first treated with an isotype antibody (control). Filledsymbols and solid lines represent mice first treated with an anti-CD226antibody.

FIG. 15 depicts a tumor growth curve of MC38-bearing wild type mice(represented by circles [∘, ●]) or TIGIT knock-out mice (represented byinverted triangles [∇▾]) treated with isotype IgGs as described inExample 7. The Y-axis depicts tumor volume in cubic millimeters and theX-axis depicts time in days post tumor challenge. Open symbols anddotted lines represent mice first treated with an isotype antibody(control). Filled symbols and solid lines represent mice first treatedwith an anti-CD226 antibody.

FIG. 16A is a cumulative distribution function (CDF) plot depicting theupregulated expression of CD226 by combination treatment in total CD8+ Tcells. The X-axis depicts CD226 expression in log 2(RPKM) (Reads PerKilobase of transcript per Million mapped reads) and the Y-axis depictscumulative frequency. The red line represents the anti-GITR/anti-PD1treatment; the black line represents isotype antibody treatment; theblue line represents anti-GITR treatment; and the purple line representsanti-PD1 treatment.

FIG. 16B is a cumulative distribution function (CDF) plot depicting theupregulated expression of CD226 by combination treatment in clonalexpanded CD8+ T cells. The X-axis depicts CD226 expression in log2(RPKM) (Reads Per Kilobase of transcript per Million mapped reads) andthe Y-axis depicts cumulative frequency. The red line represents theanti-GITR/anti-PD1 treatment; the black line represents isotype antibodytreatment; the blue line represents anti-GITR treatment; and the purpleline represents anti-PD1 treatment.

FIG. 16C is a cumulative distribution function (CDF) plot depicting theupregulated expression of CD226 by combination treatment in non-expandedCD8+ T cells. The X-axis depicts CD226 expression in log 2(RPKM) (ReadsPer Kilobase of transcript per Million mapped reads) and the Y-axisdepicts cumulative frequency. The red line represents theanti-GITR/anti-PD1 treatment; the black line represents isotype antibodytreatment; the blue line represents anti-GITR treatment; and the purpleline represents anti-PD1 treatment.

FIG. 17 is a Western blot depicting the relative expression ofphospho-CD3ζ and phospho-CD226 as a function of PD-1 concentration.

FIG. 18A is a bar chart depicting FACS analysis (number of cells) of Tcell development in thymus (Tconv, conventional T cells; DP, CD4/CD8double positive; SP, single positive; DN, CD4/CD8 double negative). Openbars represent wildtype (CD226⁺) mice. Solid filled bars represent CD226knock out (CD226^(−/−)) mice.

FIG. 18B is a bar chart depicting FACS validation (number of cells) ofthe population of T cell subsets in spleen and blood in wildtype andCD226^(−/−) animals. Open bars represent wildtype (CD226⁺) mice. Solidfilled bars represent CD226 knock out (CD226^(−/−)) mice.

FIG. 18C is a bar chart depicting FACS analysis (MFI, mean fluorescenceintensity) of T cell subsets in spleen and blood that express PD1. Openbars represent wildtype (CD226⁺) mice. Solid filled bars represent CD226knock out (CD226^(−/−)) mice.

FIG. 18D is a bar chart depicting FACS analysis (MFI) of T cell subsetsin spleen and blood that express GITR. Open bars represent wildtype(CD226⁺) mice. Solid filled bars represent CD226 knock out (CD226^(−/−))mice.

FIG. 18 E is a bar chart depicting IFN-γ secretion in picograms permilliliter upon ex vivo TCR stimulation of splenocytes withanti-CD3+anti-CD28 Ab for 16 hours. Splenocytes from CD226−/− (solidbars) or wild type (WT) (open bars) mice were stimulated withanti-CD3+anti-CD28 Ab for 16 hours.

FIG. 18 F is a bar chart depicting IL-2 secretion in picograms permilliliter upon ex vivo TCR stimulation of splenocytes withanti-CD3+anti-CD28 Ab for 16 hours. Splenocytes from CD226−/− (solidbars) or wild type (WT) (open bars) mice were stimulated withanti-CD3+anti-CD28 Ab for 16 hours.

FIG. 18 G is a bar chart depicting TNF-α secretion in picograms permilliliter upon ex vivo TCR stimulation of splenocytes withanti-CD3+anti-CD28 Ab for 16 hours. Splenocytes from CD226−/− (solidbars) or wild type (WT) (open bars) mice were stimulated withanti-CD3+anti-CD28 Ab for 16 hours.

FIG. 18 H is a bar chart depicting IL-6 secretion in picograms permilliliter upon ex vivo TCR stimulation of splenocytes withanti-CD3+anti-CD28 Ab for 16 hours. Splenocytes from CD226−/− (solidbars) or wild type (WT) (open bars) mice were stimulated withanti-CD3+anti-CD28 Ab for 16 hours.

FIG. 18 I is a bar chart depicting IL-5 secretion in picograms permilliliter upon ex vivo TCR stimulation of splenocytes withanti-CD3+anti-CD28 Ab for 16 hours. Splenocytes from CD226−/− (solidbars) or wild type (WT) (open bars) mice were stimulated withanti-CD3+anti-CD28 Ab for 16 hours.

FIG. 19A, FIG. 19B, FIG. 19C, and FIG. 19D are line graphs depictingpercent animal survival as a function of time in days post tumorchallenge. FIG. 19A depicts CD226 KO mice (rose lines) or WT littermates(black lines) challenged with MC38 tumor cells and treated with eitheranti-GITR+anti-PD-1 Ab (filled circles and squares) or isotype Abs (opencircles and squares). FIGS. 19B-19D depict the effect of antibodytreatment on (B) animals treated with antibodies blocking CD28 signaling(10 mg/kg CTLA-4-Ig; FIG. 19B, green lines); (C) animals treated withantibodies blocking OX40 signaling (10 mg/kg OX40L blocking antibody;FIG. 19C); and (D) animals treated with antibodies blocking 4-1 BBsignaling (10 mg/kg 4-1 BBL blocking antibody; FIG. 19D).

FIG. 20A is a line graph depicting tumor size (in cubic millimeters) asa function of days after tumor challenge for mice treated with isotype(open circles and black line), anti-PD1 (open squares, red line),anti-GITR (open upright pyramids and green line), and anti-GITR/anti-PD1combination therapy (open inverted pyramids and blue lines). The tumorsdepicted in FIG. 20A are MC38 tumors that do not express CD155.

FIG. 20B is a line graph depicting tumor size (in cubic millimeters) asa function of days after tumor challenge for mice treated with isotype(open circles and black line), anti-PD1 (open squares, red line),anti-GITR (open upright pyramids and green line), and anti-GITR/anti-PD1combination therapy (open inverted pyramids and blue lines). The tumorsdepicted in FIG. 20B are MC38 tumors that express CD155.

FIG. 21A is a bar chart depicting the number of cells expressing CD226from animals challenged with MC38 tumor cells over expressing CD155(filled bars) and MC38 tumor cells that do not express CD155 (openbars).

FIG. 21B is a bar chart depicting the number of cells expressing 4-1 BBfrom animals challenged with MC38 tumor cells over expressing CD155(filled bars) and MC38 tumor cells that do not express CD155 (openbars).

FIG. 21C is a bar chart depicting the number of cells expressing IFN-γ(Panel C) from animals challenged with MC38 tumor cells over expressingCD155 (filled bars) and MC38 tumor cells that do not express CD155 (openbars).

FIG. 22 depicts a dot plot RNA-seq analysis of cancer patient tumorbiopsies showing CD226 RNA expression (in log 2[RPKM]) as a function ofanti-PD-1 Ab treatment.

DETAILED DESCRIPTION

Before the present invention is described, it is to be understood thatthis invention is not limited to particular methods and experimentalconditions described, as such methods and conditions may vary. It isalso to be understood that the terminology used herein is for thepurpose of describing particular embodiments only, and is not intendedto be limiting, since the scope of the present invention will be limitedonly by the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. As used herein, the term“about,” when used in reference to a particular recited numerical value,means that the value may vary from the recited value by no more than 1%.For example, as used herein, the expression “about 100” includes 99 and101 and all values in between (e.g., 99.1, 99.2, 99.3, 99.4, etc.).

Although any methods and materials similar or equivalent to thosedescribed herein can be used in the practice or testing of the presentinvention, the preferred methods and materials are now described. Allpatents, applications and non-patent publications mentioned in thisspecification are incorporated herein by reference in their entireties.

Definitions

The expression glucocorticoid-induced tumor necrosis factor receptor,“GITR,” and the like, as used herein, refers to the humanglucocorticoid-induced tumor necrosis factor receptor, comprising theamino acid sequence as set forth in SEQ ID NO: 413 (NCBI Accession#NP_004186.1). The expression “GITR” includes both monomeric andmultimeric GITR molecules. As used herein, the expression “monomerichuman GITR” means a GITR protein or portion thereof that does notcontain or possess any multimerizing domains and that exists undernormal conditions as a single GITR molecule without a direct physicalconnection to another GITR molecule. An exemplary monomeric GITRmolecule is the molecule referred to herein as “hGITR.mmh” comprisingthe amino acid sequence of SEQ ID NO: 409 (see, e.g., Example 3,herein). As used herein, the expression “dimeric human GITR” means aconstruct comprising two GITR molecules connected to one another througha linker, covalent bond, non-covalent bond, or through a multimerizingdomain such as an antibody Fc domain. Exemplary dimeric GITR moleculesinclude those molecules referred to herein as “hGITR.mFc” and“hGITR.hFc”, comprising the amino acid sequence of SEQ ID NO: 410 andSEQ ID NO: 411 respectively (see, e.g., Example 3, herein).

All references to proteins, polypeptides and protein fragments hereinare intended to refer to the human version of the respective protein,polypeptide or protein fragment unless explicitly specified as beingfrom a non-human species. Thus, the expression “GITR” means human GITRunless specified as being from a non-human species, e.g., “mouse GITR,”“monkey GITR,” etc.

As used herein, the expression “cell surface-expressed GITR” means oneor more GITR protein(s), or the extracellular domain thereof, thatis/are expressed on the surface of a cell in vitro or in vivo, such thatat least a portion of a GITR protein is exposed to the extracellularside of the cell membrane and is accessible to an antigen-bindingportion of an antibody. A “cell surface-expressed GITR” can comprise orconsist of a GITR protein expressed on the surface of a cell whichnormally expresses GITR protein. Alternatively, “cell surface-expressedGITR” can comprise or consist of GITR protein expressed on the surfaceof a cell that normally does not express human GITR on its surface buthas been artificially engineered to express GITR on its surface.

As used herein, the expression “anti-GITR antibody” includes bothmonovalent and monospecific bivalent antibodies with a singlespecificity, as well as bispecific antibodies comprising a first armthat binds GITR and a second arm that binds a second (target) antigen,wherein the anti-GITR arm comprises any of the HCVR/LCVR or CDRsequences as set forth in Table 1 herein. The expression “anti-GITRantibody” also includes antibody-drug conjugates (ADCs) comprising ananti-GITR antibody or antigen-binding portion thereof conjugated to adrug or toxin (i.e., cytotoxic agent). The expression “anti-GITRantibody” also includes antibody-radionuclide conjugates (ARCs)comprising an anti-GITR antibody or antigen-binding portion thereofconjugated to a radionuclide.

The term “antibody”, as used herein, means any antigen-binding moleculeor molecular complex comprising at least one complementarity determiningregion (CDR) that specifically binds to or interacts with a particularantigen (e.g., GITR). The term “antibody” includes immunoglobulinmolecules comprising four polypeptide chains, two heavy (H) chains andtwo light (L) chains inter-connected by disulfide bonds, as well asmultimers thereof (e.g., IgM). Each heavy chain comprises a heavy chainvariable region (abbreviated herein as HCVR or V_(H)) and a heavy chainconstant region. The heavy chain constant region comprises threedomains, C_(H)1, C_(H)2 and C_(H)3. Each light chain comprises a lightchain variable region (abbreviated herein as LCVR or V_(L)) and a lightchain constant region. The light chain constant region comprises onedomain (C_(L)1). The V_(H) and V_(L) regions can be further subdividedinto regions of hypervariability, termed complementarity determiningregions (CDRs), interspersed with regions that are more conserved,termed framework regions (FR). Each V_(H) and V_(L) is composed of threeCDRs and four FRs, arranged from amino-terminus to carboxy-terminus inthe following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. In differentembodiments of the invention, the FRs of the anti-GITR antibody (orantigen-binding portion thereof) may be identical to the human germlinesequences, or may be naturally or artificially modified. An amino acidconsensus sequence may be defined based on a side-by-side analysis oftwo or more CDRs.

The term “antibody”, as used herein, also includes antigen-bindingfragments of full antibody molecules. The terms “antigen-bindingportion” of an antibody, “antigen-binding fragment” of an antibody, andthe like, as used herein, include any naturally occurring, enzymaticallyobtainable, synthetic, or genetically engineered polypeptide orglycoprotein that specifically binds an antigen to form a complex.Antigen-binding fragments of an antibody may be derived, e.g., from fullantibody molecules using any suitable standard techniques such asproteolytic digestion or recombinant genetic engineering techniquesinvolving the manipulation and expression of DNA encoding antibodyvariable and optionally constant domains. Such DNA is known and/or isreadily available from, e.g., commercial sources, DNA libraries(including, e.g., phage-antibody libraries), or can be synthesized. TheDNA may be sequenced and manipulated chemically or by using molecularbiology techniques, for example, to arrange one or more variable and/orconstant domains into a suitable configuration, or to introduce codons,create cysteine residues, modify, add or delete amino acids, etc.

Non-limiting examples of antigen-binding fragments include: (i) Fabfragments; (ii) F(ab′)2 fragments; (iii) Fd fragments; (iv) Fvfragments; (v) single-chain Fv (scFv) molecules; (vi) dAb fragments; and(vii) minimal recognition units consisting of the amino acid residuesthat mimic the hypervariable region of an antibody (e.g., an isolatedcomplementarity determining region (CDR) such as a CDR3 peptide), or aconstrained FR3-CDR3-FR4 peptide. Other engineered molecules, such asdomain-specific antibodies, single domain antibodies, domain-deletedantibodies, chimeric antibodies, CDR-grafted antibodies, diabodies,triabodies, tetrabodies, minibodies, nanobodies (e.g. monovalentnanobodies, bivalent nanobodies, etc.), small modularimmunopharmaceuticals (SMIPs), and shark variable IgNAR domains, arealso encompassed within the expression “antigen-binding fragment,” asused herein.

An antigen-binding fragment of an antibody will typically comprise atleast one variable domain. The variable domain may be of any size oramino acid composition and will generally comprise at least one CDRwhich is adjacent to or in frame with one or more framework sequences.In antigen-binding fragments having a V_(H) domain associated with aV_(L) domain, the V_(H) and V_(L) domains may be situated relative toone another in any suitable arrangement. For example, the variableregion may be dimeric and contain V_(H)-V_(H), V_(H)-V_(L) orV_(L)-V_(L) dimers. Alternatively, the antigen-binding fragment of anantibody may contain a monomeric V_(H) or V_(L) domain.

In certain embodiments, an antigen-binding fragment of an antibody maycontain at least one variable domain covalently linked to at least oneconstant domain. Non-limiting, exemplary configurations of variable andconstant domains that may be found within an antigen-binding fragment ofan antibody of the present invention include: (i) V_(H)-C_(H)1; (ii)V_(H)-C_(H)2; (iii) V_(H)-C_(H)3; (iv) V_(H)-C_(H)1-C_(H)2; (v)V_(H)-C_(H)1-C_(H)2-C_(H)3; (vi) V_(H)-C_(H)2-C_(H)3; (vii) V_(H)-CL;(viii) V_(L)-C_(H)1; (ix) V_(L)-C_(H)2; (X) V_(L)-C_(H)3; (xi)V_(L)-C_(H)1-C_(H)2; (xii) V_(L)-C_(H)1-C_(H)2-C_(H)3; (xiii)V_(L)-C_(H)2-C_(H)3; and (xiv) V_(L)-C_(L). In any configuration ofvariable and constant domains, including any of the exemplaryconfigurations listed above, the variable and constant domains may beeither directly linked to one another or may be linked by a full orpartial hinge or linker region. A hinge region may consist of at least 2(e.g., 5, 10, 15, 20, 40, 60 or more) amino acids which result in aflexible or semi-flexible linkage between adjacent variable and/orconstant domains in a single polypeptide molecule. Moreover, anantigen-binding fragment of an antibody of the present invention maycomprise a homo-dimer or hetero-dimer (or other multimer) of any of thevariable and constant domain configurations listed above in non-covalentassociation with one another and/or with one or more monomeric V_(H) orV_(L) domain (e.g., by disulfide bond(s)).

As with full antibody molecules, antigen-binding fragments may bemonospecific or multispecific (e.g., bispecific). A multispecificantigen-binding fragment of an antibody will typically comprise at leasttwo different variable domains, wherein each variable domain is capableof specifically binding to a separate antigen or to a different epitopeon the same antigen. Any multispecific antibody format, including theexemplary bispecific antibody formats disclosed herein, may be adaptedfor use in the context of an antigen-binding fragment of an antibody ofthe present invention using routine techniques available in the art.

The antibodies of the present invention may function throughcomplement-dependent cytotoxicity (CDC) or antibody-dependentcell-mediated cytotoxicity (ADCC). “Complement-dependent cytotoxicity”(CDC) refers to lysis of antigen-expressing cells by an antibody of theinvention in the presence of complement. “Antibody-dependentcell-mediated cytotoxicity” (ADCC) refers to a cell-mediated reaction inwhich nonspecific cytotoxic cells that express Fc receptors (FcRs)(e.g., Natural Killer (NK) cells, neutrophils, and macrophages)recognize bound antibody on a target cell and thereby lead to lysis ofthe target cell. CDC and ADCC can be measured using assays that are wellknown and available in the art. (See, e.g., U.S. Pat. Nos. 5,500,362 and5,821,337, and Clynes et al. (1998) Proc. Natl. Acad. Sci. (USA)95:652-656). The constant region of an antibody is important in theability of an antibody to fix complement and mediate cell-dependentcytotoxicity. Thus, the isotype of an antibody may be selected on thebasis of whether it is desirable for the antibody to mediatecytotoxicity.

In certain embodiments of the invention, the anti-GITR antibodies of theinvention are human antibodies. The term “human antibody”, as usedherein, is intended to include antibodies having variable and constantregions derived from human germline immunoglobulin sequences. The humanantibodies of the invention may include amino acid residues not encodedby human germline immunoglobulin sequences (e.g., mutations introducedby random or site-specific mutagenesis in vitro or by somatic mutationin vivo), for example in the CDRs and in particular CDR3. However, theterm “human antibody”, as used herein, is not intended to includeantibodies in which CDR sequences derived from the germline of anothermammalian species, such as a mouse, have been grafted onto humanframework sequences. The term “human antibody” does not includenaturally occurring molecules that normally exist without modificationor human intervention/manipulation, in a naturally occurring, unmodifiedliving organism.

The antibodies of the invention may, in some embodiments, be recombinanthuman antibodies. The term “recombinant human antibody”, as used herein,is intended to include all human antibodies that are prepared,expressed, created or isolated by recombinant means, such as antibodiesexpressed using a recombinant expression vector transfected into a hostcell (described further below), antibodies isolated from a recombinant,combinatorial human antibody library (described further below),antibodies isolated from an animal (e.g., a mouse) that is transgenicfor human immunoglobulin genes (see e.g., Taylor et al. (1992) Nucl.Acids Res. 20:6287-6295) or antibodies prepared, expressed, created orisolated by any other means that involves splicing of humanimmunoglobulin gene sequences to other DNA sequences. Such recombinanthuman antibodies have variable and constant regions derived from humangermline immunoglobulin sequences. In certain embodiments, however, suchrecombinant human antibodies are subjected to in vitro mutagenesis (or,when an animal transgenic for human Ig sequences is used, in vivosomatic mutagenesis) and thus the amino acid sequences of the V_(H) andV_(L) regions of the recombinant antibodies are sequences that, whilederived from and related to human germline V_(H) and V_(L) sequences,may not naturally exist within the human antibody germline repertoire invivo.

Human antibodies can exist in two forms that are associated with hingeheterogeneity. In one form, an immunoglobulin molecule comprises astable four chain construct of approximately 150-160 kDa in which thedimers are held together by an interchain heavy chain disulfide bond. Ina second form, the dimers are not linked via inter-chain disulfide bondsand a molecule of about 75-80 kDa is formed composed of a covalentlycoupled light and heavy chain (half-antibody). These forms have beenextremely difficult to separate, even after affinity purification.

The frequency of appearance of the second form in various intact IgGisotypes is due to, but not limited to, structural differencesassociated with the hinge region isotype of the antibody. A single aminoacid substitution in the hinge region of the human IgG4 hinge cansignificantly reduce the appearance of the second form (Angal et al.(1993) Molecular Immunology 30:105) to levels typically observed using ahuman IgG1 hinge. The instant invention encompasses antibodies havingone or more mutations in the hinge, C_(H)2 or C_(H)3 region which may bedesirable, for example, in production, to improve the yield of thedesired antibody form.

The antibodies of the invention may be isolated antibodies. An “isolatedantibody,” as used herein, means an antibody that has been identifiedand separated and/or recovered from at least one component of itsnatural environment. For example, an antibody that has been separated orremoved from at least one component of an organism, or from a tissue orcell in which the antibody naturally exists or is naturally produced, isan “isolated antibody” for purposes of the present invention. Anisolated antibody also includes an antibody in situ within a recombinantcell. Isolated antibodies are antibodies that have been subjected to atleast one purification or isolation step. According to certainembodiments, an isolated antibody may be substantially free of othercellular material and/or chemicals.

The anti-GITR antibodies disclosed herein may comprise one or more aminoacid substitutions, insertions and/or deletions in the framework and/orCDR regions of the heavy and light chain variable domains as compared tothe corresponding germline sequences from which the antibodies werederived. Such mutations can be readily ascertained by comparing theamino acid sequences disclosed herein to germline sequences availablefrom, for example, public antibody sequence databases. The presentinvention includes antibodies, and antigen-binding fragments thereof,which are derived from any of the amino acid sequences disclosed herein,wherein one or more amino acids within one or more framework and/or CDRregions are mutated to the corresponding residue(s) of the germlinesequence from which the antibody was derived, or to the correspondingresidue(s) of another human germline sequence, or to a conservativeamino acid substitution of the corresponding germline residue(s) (suchsequence changes are referred to herein collectively as “germlinemutations”). A person of ordinary skill in the art, starting with theheavy and light chain variable region sequences disclosed herein, caneasily produce numerous antibodies and antigen-binding fragments whichcomprise one or more individual germline mutations or combinationsthereof. In certain embodiments, all of the framework and/or CDRresidues within the V_(H) and/or V_(L) domains are mutated back to theresidues found in the original germline sequence from which the antibodywas derived. In other embodiments, only certain residues are mutatedback to the original germline sequence, e.g., only the mutated residuesfound within the first 8 amino acids of FR1 or within the last 8 aminoacids of FR4, or only the mutated residues found within CDR1, CDR2 orCDR3. In other embodiments, one or more of the framework and/or CDRresidue(s) are mutated to the corresponding residue(s) of a differentgermline sequence (i.e., a germline sequence that is different from thegermline sequence from which the antibody was originally derived).Furthermore, the antibodies of the present invention may contain anycombination of two or more germline mutations within the frameworkand/or CDR regions, e.g., wherein certain individual residues aremutated to the corresponding residue of a particular germline sequencewhile certain other residues that differ from the original germlinesequence are maintained or are mutated to the corresponding residue of adifferent germline sequence. Once obtained, antibodies andantigen-binding fragments that contain one or more germline mutationscan be easily tested for one or more desired property such as, improvedbinding specificity, increased binding affinity, improved or enhancedantagonistic or agonistic biological properties (as the case may be),reduced immunogenicity, etc. Antibodies and antigen-binding fragmentsobtained in this general manner are encompassed within the presentinvention.

The present invention also includes anti-GITR antibodies comprisingvariants of any of the HCVR, LCVR, and/or CDR amino acid sequencesdisclosed herein having one or more conservative substitutions. Forexample, the present invention includes anti-GITR antibodies havingHCVR, LCVR, and/or CDR amino acid sequences with, e.g., 10 or fewer, 8or fewer, 6 or fewer, 4 or fewer, etc. conservative amino acidsubstitutions relative to any of the HCVR, LCVR, and/or CDR amino acidsequences set forth in Table 1 herein.

The term “epitope” refers to an antigenic determinant that interactswith a specific antigen-binding site in the variable region of anantibody molecule known as a paratope. A single antigen may have morethan one epitope. Thus, different antibodies may bind to different areason an antigen and may have different biological effects. Epitopes may beeither conformational or linear. A conformational epitope is produced byspatially juxtaposed amino acids from different segments of the linearpolypeptide chain. A linear epitope is one produced by adjacent aminoacid residues in a polypeptide chain. In certain circumstance, anepitope may include moieties of saccharides, phosphoryl groups, orsulfonyl groups on the antigen.

The term “substantial identity” or “substantially identical,” whenreferring to a nucleic acid or fragment thereof, indicates that, whenoptimally aligned with appropriate nucleotide insertions or deletionswith another nucleic acid (or its complementary strand), there isnucleotide sequence identity in at least about 95%, and more preferablyat least about 96%, 97%, 98% or 99% of the nucleotide bases, as measuredby any well-known algorithm of sequence identity, such as FASTA, BLASTor Gap, as discussed below. A nucleic acid molecule having substantialidentity to a reference nucleic acid molecule may, in certain instances,encode a polypeptide having the same or substantially similar amino acidsequence as the polypeptide encoded by the reference nucleic acidmolecule.

As applied to polypeptides, the term “substantial similarity” or“substantially similar” means that two peptide sequences, when optimallyaligned, such as by the programs GAP or BESTFIT using default gapweights, share at least 95% sequence identity, even more preferably atleast 98% or 99% sequence identity. Preferably, residue positions whichare not identical differ by conservative amino acid substitutions. A“conservative amino acid substitution” is one in which an amino acidresidue is substituted by another amino acid residue having a side chain(R group) with similar chemical properties (e.g., charge orhydrophobicity). In general, a conservative amino acid substitution willnot substantially change the functional properties of a protein. Incases where two or more amino acid sequences differ from each other byconservative substitutions, the percent sequence identity or degree ofsimilarity may be adjusted upwards to correct for the conservativenature of the substitution. Means for making this adjustment arewell-known to those of skill in the art. See, e.g., Pearson (1994)Methods Mol. Biol. 24: 307-331, herein incorporated by reference.Examples of groups of amino acids that have side chains with similarchemical properties include (1) aliphatic side chains: glycine, alanine,valine, leucine and isoleucine; (2) aliphatic-hydroxyl side chains:serine and threonine; (3) amide-containing side chains: asparagine andglutamine; (4) aromatic side chains: phenylalanine, tyrosine, andtryptophan; (5) basic side chains: lysine, arginine, and histidine; (6)acidic side chains: aspartate and glutamate, and (7) sulfur-containingside chains are cysteine and methionine. Preferred conservative aminoacids substitution groups are: valine-leucine-isoleucine,phenylalanine-tyrosine, lysine-arginine, alanine-valine,glutamate-aspartate, and asparagine-glutamine. Alternatively, aconservative replacement is any change having a positive value in thePAM250 log-likelihood matrix disclosed in Gonnet et al. (1992) Science256: 1443-1445, herein incorporated by reference. A “moderatelyconservative” replacement is any change having a nonnegative value inthe PAM250 log-likelihood matrix.

Sequence similarity for polypeptides, which is also referred to assequence identity, is typically measured using sequence analysissoftware. Protein analysis software matches similar sequences usingmeasures of similarity assigned to various substitutions, deletions andother modifications, including conservative amino acid substitutions.For instance, GCG software contains programs such as Gap and Bestfitwhich can be used with default parameters to determine sequence homologyor sequence identity between closely related polypeptides, such ashomologous polypeptides from different species of organisms or between awild type protein and a mutein thereof. See, e.g., GCG Version 6.1.Polypeptide sequences also can be compared using FASTA using default orrecommended parameters, a program in GCG Version 6.1. FASTA (e.g.,FASTA2 and FASTA3) provides alignments and percent sequence identity ofthe regions of the best overlap between the query and search sequences(Pearson (2000) supra). Another preferred algorithm when comparing asequence of the invention to a database containing a large number ofsequences from different organisms is the computer program BLAST,especially BLASTP or TBLASTN, using default parameters. See, e.g.,Altschul et al. (1990) J. Mol. Biol. 215:403-410 and Altschul et al.(1997) Nucleic Acids Res. 25:3389-402, each herein incorporated byreference.

Anti-GITR Antibodies Comprising Fc Variants

According to certain embodiments of the present invention, anti-GITRantibodies are provided comprising an Fc domain comprising one or moremutations which enhance or diminish antibody binding to the FcRnreceptor, e.g., at acidic pH as compared to neutral pH. For example, thepresent invention includes anti-GITR antibodies comprising a mutation inthe C_(H)2 or a C_(H)3 region of the Fc domain, wherein the mutation(s)increases the affinity of the Fc domain to FcRn in an acidic environment(e.g., in an endosome where pH ranges from about 5.5 to about 6.0). Suchmutations may result in an increase in serum half-life of the antibodywhen administered to an animal. Non-limiting examples of such Fcmodifications include, e.g., a modification at position 250 (e.g., E orQ); 250 and 428 (e.g., L or F); 252 (e.g., L/Y/F/W or T), 254 (e.g., Sor T), and 256 (e.g., S/R/Q/E/D or T); or a modification at position 428and/or 433 (e.g., H/L/R/S/P/Q or K) and/or 434 (e.g., H/F or Y); or amodification at position 250 and/or 428; or a modification at position307 or 308 (e.g., 308F, V308F), and 434. In one embodiment, themodification comprises a 428L (e.g., M428L) and 434S (e.g., N434S)modification; a 428L, 2591 (e.g., V2591), and 308F (e.g., V308F)modification; a 433K (e.g., H433K) and a 434 (e.g., 434Y) modification;a 252, 254, and 256 (e.g., 252Y, 254T, and 256E) modification; a 2500and 428L modification (e.g., T250Q and M428L); and a 307 and/or 308modification (e.g., 308F or 308P).

For example, the present invention includes anti-GITR antibodiescomprising an Fc domain comprising one or more pairs or groups ofmutations selected from the group consisting of: 2500 and 248L (e.g.,T250Q and M248L); 252Y, 254T and 256E (e.g., M252Y, S254T and T256E);428L and 434S (e.g., M428L and N434S); and 433K and 434F (e.g., H433Kand N434F). All possible combinations of the foregoing Fc domainmutations, and other mutations within the antibody variable domainsdisclosed herein, are contemplated within the scope of the presentinvention.

Biological Characteristics of the Anti-GITR Antibodies

The present invention includes antibodies and antigen-binding fragmentsthereof that bind monomeric human GITR with high affinity. For example,the present invention includes anti-GITR antibodies that bind monomerichuman GITR (e.g., hGITR.mmh) with a K_(D) of less than about 5.0 nM asmeasured by surface plasmon resonance at 37° C., e.g., using an assayformat as defined in Example 3 herein, or a substantially similar assay.In some embodiments, anti-GITR antibodies are provided that bindmonomeric human GITR at 37° C. with a K_(D) of less than about 4 nM,less than about 3 nM, less than about 2 nM, or less than about 1.50 nMas measured by surface plasmon resonance, e.g., using an assay format asdefined in Example 3 herein, or a substantially similar assay.

The present invention also includes antibodies and antigen-bindingfragments thereof that bind monomeric human GITR (e.g., hGITR.mmh) witha dissociative half-life (t½) of greater than about 12 minutes asmeasured by surface plasmon resonance at 37° C., e.g., using an assayformat as defined in Example 3 herein, or a substantially similar assay.According to certain embodiments, anti-GITR antibodies are provided thatbind monomeric human GITR at 37° C. with a t½ of greater than about 12minutes, greater than about 13 minutes, greater than about 14 minutes,greater than about 15 minutes, or longer, as measured by surface plasmonresonance, e.g., using an assay format as defined in Example 3 herein,or a substantially similar assay.

The present invention also includes antibodies and antigen-bindingfragments thereof that bind dimeric human GITR (e.g., hGITR.mFc) withhigh affinity. For example, the present invention includes anti-GITRantibodies that bind dimeric human GITR with a K_(D) of less than about950 pM as measured by surface plasmon resonance at 37° C., e.g., usingan assay format as defined in Example 3 herein, or a substantiallysimilar assay. According to certain embodiments, anti-GITR antibodiesare provided that bind dimeric human GITR at 37° C. with a K_(D) of lessthan about 900 pM, less than about 850 pM, less than about 800 pM, lessthan about 700 pM, less than about 600 pM, less than about 500 pM, lessthan about 400 pM, less than about 300 pM, less than about 200 pM, orless than about 100 pM as measured by surface plasmon resonance, e.g.,using an assay format as defined in Example 3 herein, or a substantiallysimilar assay.

The present invention also includes antibodies and antigen-bindingfragments thereof that bind dimeric human GITR (e.g., hGITR.mFc) with adissociative half-life (t½) of greater than about 7 minutes as measuredby surface plasmon resonance at 37° C., e.g., using an assay format asdefined in Example 3 herein, or a substantially similar assay. Accordingto certain embodiments, anti-GITR antibodies are provided that binddimeric human GITR at 37° C. with a t½ of greater than about 10 minutes,greater than about 20 minutes, greater than about 30 minutes, greaterthan about 40 minutes, greater than about 50 minutes, greater than about60 minutes, greater than about 70 minutes, greater than about 80minutes, greater than about 90 minutes, greater than about 100 minutes,or longer, as measured by surface plasmon resonance, e.g., using anassay format as defined in Example 3 herein, or a substantially similarassay.

The present disclosure also includes antibodies and antigen-bindingfragments thereof that bind cell-surface-expressed GITR. For example,antibodies that bind to human GITR transfected embryonic kidney 293(HEK-293) D9 cells with high affinity are provided herein. For example,the instant disclosure includes anti-GITR antibodies that bind humanGITR transfected embryonic kidney 293 (HEK-293) D9 cells with an EC₅₀ ofless than about 260 pM as measured by electrochemiluminescence, e.g.,using an assay format as defined in Example 4 herein, or a substantiallysimilar assay. In certain embodiments, anti-GITR antibodies are providedthat bind human GITR transfected embryonic kidney 293 (HEK-293) D9 cellswith an EC₅₀ of less than about 250 pM, less than about 240 pM, lessthan about 230 pM, or less than about 220 pM as measured byelectrochemiluminescence, e.g., using an assay format as defined inExample 4 herein, or a substantially similar assay.

The antibodies of the present invention may possess one or more of theaforementioned biological characteristics, or any combination thereof.The foregoing list of biological characteristics of the antibodies ofthe invention is not intended to be exhaustive. Other biologicalcharacteristics of the antibodies of the present invention will beevident to a person of ordinary skill in the art from a review of thepresent disclosure including the working Examples herein.

Fc Anchoring-Dependent and Anchoring-Independent GITR Activation andGITRL Blocking

The present disclosure includes antibodies and antigen-binding fragmentsthereof that activate human GITR, e.g., as determined in the assayformats described in Example 5 and/or Example 6 herein, or in asubstantially similar assay format. As used herein, “activates humanGITR” refers to the activation of GITR via binding to its cognateligand, GITR Ligand (GITRL) or to the binding of agonist anti-GITRantigen binding protein(s) to GITR. With regard to activation of GITR byagonist anti-GITR binding proteins, “activation” can be in the presenceor absence of antigen-binding protein anchoring to Fc gamma receptors.Human GITR activation is manifested in the exhibition of certainbiological activities, including but not limited to the induction orenhancement of GITR signaling in vitro or in vivo, the reduction ofregulatory T cell suppression of effector T cell activity; the decreaseof circulating T reg levels in vitro or in vivo, the decrease ofintratumoral T regs in vivo, the activation of effector T cells in vitroor in vivo, the induction or enhancement of effector T cellproliferation in vitro or in vivo, or the inhibition or reduction oftumor growth in vivo.

GITR Activation in the Absence of Fc Anchoring

In some embodiments, the antibodies and antigen-binding fragmentsthereof provided herein activate human GITR in the absence of Fcanchoring, e.g., as determined in the assay formats described in Example5 and/or Example 6 herein, or in a substantially similar assay format.As used herein, “in the absence of Fc anchoring” refers to theactivation of GITR and GITR-mediated signaling or blocking of GITRLwithout the clustering of anti-GITR antibodies by different forms of theFc gamma receptor and can be determined and quantified via, e.g., theactivation of primary T-cells co-cultured in vitro in the absence ofcell-surface bound Fc gamma receptor(s). In some embodiments, theantibody or antigen-binding fragment thereof activates human GITR at anactivation percentage greater than about 25% at an EC₅₀ of less thanabout 3 nM in the absence of Fc anchoring, as determined by NFκBreporter assay, e.g., as described in Example 5 or substantially similarassay format. In some embodiments, the antibody or antigen-bindingfragment thereof activates human GITR at an activation percentagegreater than about 30%, greater than about 40%, greater than about 50%,greater than about 60%, or greater than about 65% at an EC₅₀ of lessthan about 3 nM in the absence of Fc anchoring as determined by NFκBreporter assay, e.g., as described in Example 5 or substantially similarassay format. In some embodiments, the antibody or antigen-bindingfragment thereof activates human GITR at an activation percentagegreater than about 30%, greater than about 40%, greater than about 50%,greater than about 60%, or greater than about 65% at an EC₅₀ of lessthan about 2 nM in the absence of Fc anchoring as determined by NFκBreporter assay, e.g., as described in Example 5 or substantially similarassay format. In some embodiments, the antibody or antigen-bindingfragment thereof activates human GITR at an activation percentagegreater than about 30%, greater than about 40%, greater than about 50%,greater than about 60%, or greater than about 65% at an EC₅₀ of lessthan about 1.5 nM in the absence of Fc anchoring as determined by NFκBreporter assay, e.g., as described in Example 5 or substantially similarassay format. In some embodiments, the antibody or antigen-bindingfragment thereof activates human GITR at an activation percentagegreater than about 30%, greater than about 40%, greater than about 50%,greater than about 60%, or greater than about 65% at an EC₅₀ of lessthan about 1.4 nM in the absence of Fc anchoring as determined by NFκBreporter assay, e.g., as described in Example 5 or substantially similarassay format. In some embodiments, the antibody or antigen-bindingfragment thereof activates human GITR at an activation percentagegreater than about 30%, greater than about 40%, greater than about 50%,greater than about 60%, or greater than about 65% at an EC₅₀ of lessthan about 1.3 nM in the absence of Fc anchoring as determined by NFκBreporter assay, e.g., as described in Example 5 or substantially similarassay format.

In some embodiments, the antibody or antigen-binding fragment thereofbinds GITR and exhibits T-cell proliferative activity in the absence ofFc-anchoring as determined by naïve human CD4+ T-cell proliferationassay, e.g., as described in Example 6 or substantially similar assayformat. In some embodiments, the antibody or antigen-binding fragmentthereof binds GITR and exhibits T-cell proliferative activity in theabsence of Fc anchoring with an EC₅₀ of about 8 nM or less as determinedby naïve human CD4+ T-cell proliferation assay, e.g., as described inExample 6 or substantially similar assay format. In some embodiments,the antibody or antigen-binding fragment thereof binds GITR and exhibitsT-cell proliferative activity in the absence of Fc anchoring at least 2,at least 3, at least 4, at least 5, at least 6, at least 7, at least 8,at least 9, at least 10, or at least 11 fold above background at about22 nM antibody (or antigen-binding fragment) concentration as determinedby naïve human CD4+ T-cell proliferation assay, e.g., as described inExample 6 or substantially similar assay format.

GITR Activation in the Presence of Fc Anchoring

In some embodiments, the antibodies or antigen-binding fragments thereofprovided herein activate human GITR in the presence of Fc anchoring,e.g., as determined in the assay formats described in Example 5 and/orExample 6 herein, or in a substantially similar assay format. As usedherein, “in the presence of Fc anchoring” refers to the activation ofGITR and GITR mediated signaling or blocking of GITRL through theclustering of anti-GITR antibodies via the interaction of the Fc regionof the antibodies with different forms of the Fc gamma receptor (FcgR),such as FcgRI, FcgRIIa or FcgRIIIa and can be determined and quantifiedvia, e.g., the activation of T-cells co-cultured in vitro in thepresence of cell-surface bound Fc gamma receptor(s).

In some embodiments, the antibody or antigen-binding fragment thereofexhibits T-cell proliferative activity in the presence of Fc anchoringat least about 2 fold above background at about 33 nM antibody (orantibody-binding fragment) concentration as determined by naïve humanCD4+ T-cell proliferation assay, e.g., as described in Example 6 orsubstantially similar assay format. In some embodiments, the antibody orantigen-binding fragment thereof exhibits T-cell proliferative activityin the presence of Fc anchoring at least about 2 fold, at least about 3fold, at least about 4 fold, or at least about 5 fold above backgroundat about 33 nM antibody (or antigen-binding fragment) concentration asdetermined by naïve human CD4+ T-cell proliferation assay, e.g., asdescribed in Example 6 or substantially similar assay format. In someembodiments, the antibody or antigen-binding fragment exhibits T-cellproliferative activity in the presence of Fc anchoring with an EC₅₀ ofless than about 34 nM as determined by naïve human CD4+ T-cellproliferation assay, e.g., as described in Example 6 or substantiallysimilar assay format. In some embodiments, the antibody orantigen-binding fragment exhibits T-cell proliferative activity in thepresence of Fc anchoring with an EC₅₀ of less than about 30 nM, lessthan about 20 nM, less than about 10 nM, less than about 5 nM, or lessthan about 4 nM as determined by naïve human CD4+ T-cell proliferationassay, e.g., as described in Example 6 or substantially similar assayformat.

Antibodies that Block GITR Ligand Mediated Receptor Stimulation

The present disclosure includes antibodies that block human GITR ligand(hGITRL)-mediated receptor stimulation, e.g., as determined in the assayformat described in Example 5 herein. As used herein, “blocks human GITRligand (hGITRL)-mediated receptor stimulation” refers to the ability ofanti-GITR antigen binding proteins to block the binding of GITR to itscognate ligand, GITRL. The blocking of GITR ligand can restore thesuppression of effector T-cell activity by regulatory T cells. Theblocking of GITR ligand can be determined and quantified via a varietyof methods known in the art, including, for example, the reduction inT-cell proliferation or cytokine secretion and an increase in the levelsof circulating regulatory T cells.

In some embodiments, the antibodies provided herein block human GITRligand (hGITRL)-mediated receptor stimulation in the absence of GITRanchoring, e.g., as determined in the assay format described in Example5 herein. In some embodiments, the antibody or antibody-binding fragmentthereof blocks human GITR ligand-mediated receptor stimulation in theabsence of Fc anchoring with a blocking percentage greater than about55% at an IC₅₀ less than about 4.0 nM as determined by NFκB reporterassay, e.g., as described in Example 5 or substantially similar assayformat. In some embodiments, the antibody or antibody-binding fragmentthereof blocks human GITR ligand-mediated receptor stimulation in theabsence of Fc anchoring with a blocking percentage greater than about60%, greater than about 70%, greater than about 80%, or greater thanabout 85% at an IC₅₀ less than about 4.0 nM, less than about 3.0 nM,less than about 2.0 nM, less than about 1.0 nM, less than about 0.9 nM,less than about 0.8 nM, or less than about 0.7 nM as determined by NFκBreporter assay, e.g., as described in Example 5 or substantially similarassay format.

In some embodiments, the antibodies or antigen binding fragmentsactivates human GITR and blocks human GITR ligand-mediated receptorstimulation at a blocking percentage less than about 25% in the absenceof Fc anchoring as determined by NFκB reporter assay, e.g., in the assaydescribed in Example 5 or substantially similar assay. In someembodiments, the antibodies or antigen binding fragments activates humanGITR and blocks human GITR ligand-mediated receptor stimulation at ablocking percentage less than about 54% in the absence of Fc anchoringas determined by NFκB reporter assay, e.g., in the assay described inExample 5 or substantially similar assay. In some embodiments, theantibodies or antigen binding fragments activates human GITR and blockshuman GITR ligand-mediated receptor stimulation at a blocking percentageless than about 40%, less than about 30%, less than about 20%, less thanabout 10%, less than about 5%, or less than about 1% in the absence ofFc anchoring as determined by NFκB reporter assay, e.g., in the assaydescribed in Example 5 or substantially similar assay. In someembodiments, the antibodies or antigen binding fragments activates humanGITR at an activation percentage of at least about 50% and does notblock hGITRL-mediated receptor stimulation at a blocking percentage ofgreater than about 50% in the absence of Fc anchoring as determined byNFκB reporter assay, e.g., in the assay described in Example 5 orsubstantially similar assay.

In some embodiments, the antibodies or antigen binding fragments bothactivate human GITR and block human GITR ligand (hGITRL)-mediatedreceptor stimulation.

In some embodiments, the antibodies both activate human GITR and blockhuman GITR ligand (hGITRL)-mediated receptor stimulation in the absenceof Fc anchoring, e.g., as determined in the assay format described inexample 5 herein, or a substantially similar assay. In some embodiments,

-   -   (A) the antibody or antigen-binding fragment possesses at least        one of the properties selected from the group consisting of:        -   i. activates human GITR in the absence of Fc anchoring at an            activation percentage greater than about 25% at an EC₅₀ less            than about 3 nM as determined by NFκB reporter assay and        -   ii. activates human GITR in the absence of Fc anchoring with            an EC₅₀ of less than about 1.0 nM as determined by NFκB            reporter assay; and    -   (B) the antibody or antigen-binding fragment blocks        hGITRL-mediated receptor stimulation in the absence of Fc        anchoring at a blocking percentage greater than about 54% at an        IC₅₀ of less than about 4.0 nM as determined by NFκB reporter        assay.

In some embodiments,

-   -   (A) the antibody or antigen-binding fragment activates human        GITR in the absence of Fc anchoring at an activation percentage        greater than about 50% at an EC₅₀ less than about 1.5 nM as        determined by NFκB reporter assay; and    -   (B) the antibody or antigen-binding fragment blocks        hGITRL-mediated receptor stimulation in the absence of Fc        anchoring at a blocking percentage greater than about 54% at an        IC₅₀ of less than about 4.0 nM as determined by NFκB reporter        assay; and

Epitope Mapping and Related Technologies

The epitope to which the antibodies of the present invention bind mayconsist of a single contiguous sequence of 3 or more (e.g., 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more) amino acidsof a GITR protein. Alternatively, the epitope may consist of a pluralityof non-contiguous amino acids (or amino acid sequences) of GITR. In someembodiments, the epitope is located on or near the GITRL-binding domainof GITR. In other embodiments, the epitope is located outside of theGITRL-binding domain of GITR, e.g., at a location on the surface of GITRat which an antibody, when bound to such an epitope, does not interferewith GITRL binding to GITR.

Various techniques known to persons of ordinary skill in the art can beused to determine whether an antibody “interacts with one or more aminoacids” within a polypeptide or protein. Exemplary techniques include,e.g., routine cross-blocking assay such as that described Antibodies,Harlow and Lane (Cold Spring Harbor Press, Cold Spring Harb., N.Y.),alanine scanning mutational analysis, peptide blots analysis (Reineke,2004, Methods Mol Biol 248:443-463), and peptide cleavage analysis. Inaddition, methods such as epitope excision, epitope extraction andchemical modification of antigens can be employed (Tomer, 2000, ProteinScience 9:487-496). Another method that can be used to identify theamino acids within a polypeptide with which an antibody interacts ishydrogen/deuterium exchange detected by mass spectrometry. In generalterms, the hydrogen/deuterium exchange method involvesdeuterium-labeling the protein of interest, followed by binding theantibody to the deuterium-labeled protein. Next, the protein/antibodycomplex is transferred to water to allow hydrogen-deuterium exchange tooccur at all residues except for the residues protected by the antibody(which remain deuterium-labeled). After dissociation of the antibody,the target protein is subjected to protease cleavage and massspectrometry analysis, thereby revealing the deuterium-labeled residueswhich correspond to the specific amino acids with which the antibodyinteracts. See, e.g., Ehring (1999) Analytical Biochemistry267(2):252-259; Engen and Smith (2001) Anal. Chem. 73:256A-265A.

The present invention further includes anti-GITR antibodies that bind tothe same epitope as any of the specific exemplary antibodies describedherein (e.g. antibodies comprising any of the amino acid sequences asset forth in Table 1 herein). Likewise, the present invention alsoincludes anti-GITR antibodies that compete for binding to GITR with anyof the specific exemplary antibodies described herein (e.g. antibodiescomprising any of the amino acid sequences as set forth in Table 1herein).

One can easily determine whether an antibody binds to the same epitopeas, or competes for binding with, a reference anti-GITR antibody byusing routine methods known in the art and exemplified herein. Forexample, to determine if a test antibody binds to the same epitope as areference anti-GITR antibody of the invention, the reference antibody isallowed to bind to a GITR protein. Next, the ability of a test antibodyto bind to the GITR molecule is assessed. If the test antibody is ableto bind to GITR following saturation binding with the referenceanti-GITR antibody, it can be concluded that the test antibody binds toa different epitope than the reference anti-GITR antibody. On the otherhand, if the test antibody is not able to bind to the GITR moleculefollowing saturation binding with the reference anti-GITR antibody, thenthe test antibody may bind to the same epitope as the epitope bound bythe reference anti-GITR antibody of the invention. Additional routineexperimentation (e.g., peptide mutation and binding analyses) can thenbe carried out to confirm whether the observed lack of binding of thetest antibody is in fact due to binding to the same epitope as thereference antibody or if steric blocking (or another phenomenon) isresponsible for the lack of observed binding. Experiments of this sortcan be performed using ELISA, RIA, Biacore, flow cytometry or any otherquantitative or qualitative antibody-binding assay available in the art.In accordance with certain embodiments of the present invention, twoantibodies bind to the same (or overlapping) epitope if, e.g., a 1-, 5-,10-, 20- or 100-fold excess of one antibody inhibits binding of theother by at least 50% but preferably 75%, 90% or even 99% as measured ina competitive binding assay (see, e.g., Junghans et al., Cancer Res.1990:50:1495-1502). Alternatively, two antibodies are deemed to bind tothe same epitope if essentially all amino acid mutations in the antigenthat reduce or eliminate binding of one antibody reduce or eliminatebinding of the other. Two antibodies are deemed to have “overlappingepitopes” if only a subset of the amino acid mutations that reduce oreliminate binding of one antibody reduce or eliminate binding of theother.

To determine if an antibody competes for binding (or cross-competes forbinding) with a reference anti-GITR antibody, the above-describedbinding methodology is performed in two orientations: In a firstorientation, the reference antibody is allowed to bind to a GITR proteinunder saturating conditions followed by assessment of binding of thetest antibody to the GITR molecule. In a second orientation, the testantibody is allowed to bind to a GITR molecule under saturatingconditions followed by assessment of binding of the reference antibodyto the GITR molecule. If, in both orientations, only the first(saturating) antibody is capable of binding to the GITR molecule, thenit is concluded that the test antibody and the reference antibodycompete for binding to GITR. As will be appreciated by a person ofordinary skill in the art, an antibody that competes for binding with areference antibody may not necessarily bind to the same epitope as thereference antibody, but may sterically block binding of the referenceantibody by binding an overlapping or adjacent epitope.

Preparation of Human Antibodies

The anti-GITR antibodies of the present invention can be fully humanantibodies. Methods for generating monoclonal antibodies, includingfully human monoclonal antibodies are known in the art. Any such knownmethods can be used in the context of the present invention to makehuman antibodies that specifically bind to human GITR.

Using VELOCIMMUNE™ technology, for example, or any other similar knownmethod for generating fully human monoclonal antibodies, high affinitychimeric antibodies to GITR are initially isolated having a humanvariable region and a mouse constant region. As in the experimentalsection below, the antibodies are characterized and selected fordesirable characteristics, including affinity, ligand blocking activity,selectivity, epitope, etc. If necessary, mouse constant regions arereplaced with a desired human constant region, for example wild-type ormodified IgG1 or IgG4, to generate a fully human anti-GITR antibody.While the constant region selected may vary according to specific use,high affinity antigen-binding and target specificity characteristicsreside in the variable region. In certain instances, fully humananti-GITR antibodies are isolated directly from antigen-positive Bcells.

Bioequivalents

The anti-GITR antibodies and antibody fragments of the present inventionencompass proteins having amino acid sequences that vary from those ofthe described antibodies but that retain the ability to bind human GITR.Such variant antibodies and antibody fragments comprise one or moreadditions, deletions, or substitutions of amino acids when compared toparent sequence, but exhibit biological activity that is essentiallyequivalent to that of the described antibodies. Likewise, the anti-GITRantibody-encoding DNA sequences of the present invention encompasssequences that comprise one or more additions, deletions, orsubstitutions of nucleotides when compared to the disclosed sequence,but that encode an anti-GITR antibody or antibody fragment that isessentially bioequivalent to an anti-GITR antibody or antibody fragmentof the invention. Examples of such variant amino acid and DNA sequencesare discussed above.

Two antigen-binding proteins, or antibodies, are consideredbioequivalent if, for example, they are pharmaceutical equivalents orpharmaceutical alternatives whose rate and extent of absorption do notshow a significant difference when administered at the same molar doseunder similar experimental conditions, either single dose or multipledose. Some antibodies will be considered equivalents or pharmaceuticalalternatives if they are equivalent in the extent of their absorptionbut not in their rate of absorption and yet may be consideredbioequivalent because such differences in the rate of absorption areintentional and are reflected in the labeling, are not essential to theattainment of effective body drug concentrations on, e.g., chronic use,and are considered medically insignificant for the particular drugproduct studied.

In one embodiment, two antigen-binding proteins are bioequivalent ifthere are no clinically meaningful differences in their safety, purity,and potency.

In one embodiment, two antigen-binding proteins are bioequivalent if apatient can be switched one or more times between the reference productand the biological product without an expected increase in the risk ofadverse effects, including a clinically significant change inimmunogenicity, or diminished effectiveness, as compared to continuedtherapy without such switching.

In one embodiment, two antigen-binding proteins are bioequivalent ifthey both act by a common mechanism or mechanisms of action for thecondition or conditions of use, to the extent that such mechanisms areknown.

Bioequivalence may be demonstrated by in vivo and in vitro methods.Bioequivalence measures include, e.g., (a) an in vivo test in humans orother mammals, in which the concentration of the antibody or itsmetabolites is measured in blood, plasma, serum, or other biologicalfluid as a function of time; (b) an in vitro test that has beencorrelated with and is reasonably predictive of human in vivobioavailability data; (c) an in vivo test in humans or other mammals inwhich the appropriate acute pharmacological effect of the antibody (orits target) is measured as a function of time; and (d) in awell-controlled clinical trial that establishes safety, efficacy, orbioavailability or bioequivalence of an antibody.

Bioequivalent variants of anti-GITR antibodies of the invention may beconstructed by, for example, making various substitutions of residues orsequences or deleting terminal or internal residues or sequences notneeded for biological activity. For example, cysteine residues notessential for biological activity can be deleted or replaced with otheramino acids to prevent formation of unnecessary or incorrectintramolecular disulfide bridges upon renaturation. In other contexts,bioequivalent antibodies may include anti-GITR antibody variantscomprising amino acid changes which modify the glycosylationcharacteristics of the antibodies, e.g., mutations which eliminate orremove glycosylation.

Species Selectivity and Species Cross-Reactivity

The present invention, according to certain embodiments, providesanti-GITR antibodies that bind to human GITR but not to GITR from otherspecies. The present invention also includes anti-GITR antibodies thatbind to human GITR and to GITR from one or more non-human species. Forexample, the anti-GITR antibodies of the invention may bind to humanGITR and may bind or not bind, as the case may be, to one or more ofmouse, rat, guinea pig, hamster, gerbil, pig, cat, dog, rabbit, goat,sheep, cow, horse, camel, cynomologous, marmoset, rhesus or chimpanzeeGITR. According to certain exemplary embodiments of the presentinvention, anti-GITR antibodies are provided which specifically bindhuman GITR and cynomolgus monkey (e.g., Macaca fascicularis) GITR. Otheranti-GITR antibodies of the invention bind human GITR but do not bind,or bind only weakly, to cynomolgus monkey GITR.

Multispecific Antibodies

The antibodies of the present invention may be monospecific ormultispecific (e.g., bispecific). Multispecific antibodies may bespecific for different epitopes of one target polypeptide or may containantigen-binding domains specific for more than one target polypeptide.See, e.g., Tutt et al., 1991, J. Immunol. 147:60-69; Kufer et al., 2004,Trends Biotechnol. 22:238-244. The anti-GITR antibodies of the presentinvention can be linked to or co-expressed with another functionalmolecule, e.g., another peptide or protein. For example, an antibody orfragment thereof can be functionally linked (e.g., by chemical coupling,genetic fusion, noncovalent association or otherwise) to one or moreother molecular entities, such as another antibody or antibody fragmentto produce a bispecific or a multispecific antibody with a secondbinding specificity.

The present invention includes bispecific antibodies wherein one arm ofan immunoglobulin binds human GITR, and the other arm of theimmunoglobulin is specific for a second antigen. The GITR-binding armcan comprise any of the HCVR/LCVR or CDR amino acid sequences as setforth in Table 1 herein. In certain embodiments, the GITR-binding armbinds human GITR and blocks GITRL binding to GITR. In other embodiments,the GITR-binding arm binds human GITR but does not block GITRL bindingto GITR. In some embodiments, the GITR binding arm binds human GITR andactivates GITR signaling. In other embodiments, the GITR binding armblocks GITRL mediated receptor stimulation. The present invention alsoincludes bispecific antibodies wherein one arm of an antibody binds afirst epitope of human GITR, and the other arm of said antibody binds asecond distinct epitope of human GITR.

An exemplary bispecific antibody format that can be used in the contextof the present invention involves the use of a first immunoglobulin (Ig)C_(H)3 domain and a second Ig C_(H)3 domain, wherein the first andsecond Ig C_(H)3 domains differ from one another by at least one aminoacid, and wherein at least one amino acid difference reduces binding ofthe bispecific antibody to Protein A as compared to a bispecificantibody lacking the amino acid difference. In one embodiment, the firstIg C_(H)3 domain binds Protein A and the second Ig C_(H)3 domaincontains a mutation that reduces or abolishes Protein A binding such asan H95R modification (by IMGT exon numbering; H435R by EU numbering).The second C_(H)3 may further comprise a Y96F modification (by IMGT;Y436F by EU). Further modifications that may be found within the secondC_(H)3 include: D16E, L18M, N44S, K52N, V57M, and V82I (by IMGT; D356E,L358M, N384S, K392N, V397M, and V422I by EU) in the case of IgG1antibodies; N44S, K52N, and V82I (IMGT; N384S, K392N, and V422I by EU)in the case of IgG2 antibodies; and Q15R, N44S, K52N, V57M, R69K, E79Q,and V82I (by IMGT; Q355R, N384S, K392N, V397M, R409K, E419Q, and V422Iby EU) in the case of IgG4 antibodies. Variations on the bispecificantibody format described above are contemplated within the scope of thepresent invention.

Other exemplary bispecific formats that can be used in the context ofthe present invention include, without limitation, e.g., scFv-based ordiabody bispecific formats, IgG-scFv fusions, dual variable domain(DVD)-Ig, Quadroma, knobs-into-holes, common light chain (e.g., commonlight chain with knobs-into-holes, etc.), CrossMab, CrossFab,(SEED)body, leucine zipper, Duobody, IgG1/IgG2, dual acting Fab(DAF)-IgG, and Mab² bispecific formats (see, e.g., Klein et al. 2012,mAbs 4:6, 1-11, and references cited therein, for a review of theforegoing formats). Bispecific antibodies can also be constructed usingpeptide/nucleic acid conjugation, e.g., wherein unnatural amino acidswith orthogonal chemical reactivity are used to generate site-specificantibody-oligonucleotide conjugates which then self-assemble intomultimeric complexes with defined composition, valency and geometry.(See, e.g., Kazane et al., J. Am. Chem. Soc. [Epub: Dec. 4, 2012]).

Therapeutic Formulation and Administration

The invention provides pharmaceutical compositions comprising theanti-GITR antibodies or antigen-binding fragments thereof of the presentinvention. The pharmaceutical compositions of the invention areformulated with suitable carriers, excipients, and other agents thatprovide improved transfer, delivery, tolerance, and the like. Amultitude of appropriate formulations can be found in the formularyknown to all pharmaceutical chemists: Remington's PharmaceuticalSciences, Mack Publishing Company, Easton, Pa. These formulationsinclude, for example, powders, pastes, ointments, jellies, waxes, oils,lipids, lipid (cationic or anionic) containing vesicles (such asLIPOFECTIN™, Life Technologies, Carlsbad, Calif.), DNA conjugates,anhydrous absorption pastes, oil-in-water and water-in-oil emulsions,emulsions carbowax (polyethylene glycols of various molecular weights),semi-solid gels, and semi-solid mixtures containing carbowax. See alsoPowell et al. “Compendium of excipients for parenteral formulations” PDA(1998) J Pharm Sci Technol 52:238-311.

The dose of antibody administered to a patient may vary depending uponthe age and the size of the patient, target disease, conditions, routeof administration, and the like. The preferred dose is typicallycalculated according to body weight or body surface area. In an adultpatient, it may be advantageous to intravenously administer the antibodyof the present invention normally at a single dose of about 0.01 toabout 20 mg/kg body weight, more preferably about 0.02 to about 7, about0.03 to about 5, or about 0.05 to about 3 mg/kg body weight. Dependingon the severity of the condition, the frequency and the duration of thetreatment can be adjusted. Effective dosages and schedules foradministering anti-GITR antibodies may be determined empirically; forexample, patient progress can be monitored by periodic assessment, andthe dose adjusted accordingly. Moreover, interspecies scaling of dosagescan be performed using well-known methods in the art (e.g., Mordenti etal., 1991, Pharmaceut. Res. 8:1351).

Various delivery systems are known and can be used to administer thepharmaceutical composition of the invention, e.g., encapsulation inliposomes, microparticles, microcapsules, recombinant cells capable ofexpressing the mutant viruses, receptor mediated endocytosis (see, e.g.,Wu et al., 1987, J. Biol. Chem. 262:4429-4432). Methods of introductioninclude, but are not limited to, intradermal, intramuscular,intraperitoneal, intravenous, subcutaneous, intranasal, epidural, andoral routes. The composition may be administered by any convenientroute, for example by infusion or bolus injection, by absorption throughepithelial or mucocutaneous linings (e.g., oral mucosa, rectal andintestinal mucosa, etc.) and may be administered together with otherbiologically active agents. Administration can be systemic or local.

A pharmaceutical composition of the present invention can be deliveredsubcutaneously or intravenously with a standard needle and syringe. Inaddition, with respect to subcutaneous delivery, a pen delivery devicereadily has applications in delivering a pharmaceutical composition ofthe present invention. Such a pen delivery device can be reusable ordisposable. A reusable pen delivery device generally utilizes areplaceable cartridge that contains a pharmaceutical composition. Onceall of the pharmaceutical composition within the cartridge has beenadministered and the cartridge is empty, the empty cartridge can readilybe discarded and replaced with a new cartridge that contains thepharmaceutical composition. The pen delivery device can then be reused.In a disposable pen delivery device, there is no replaceable cartridge.Rather, the disposable pen delivery device comes prefilled with thepharmaceutical composition held in a reservoir within the device. Oncethe reservoir is emptied of the pharmaceutical composition, the entiredevice is discarded.

Numerous reusable pen and autoinjector delivery devices haveapplications in the subcutaneous delivery of a pharmaceuticalcomposition of the present invention. Examples include, but are notlimited to AUTOPEN™ (Owen Mumford, Inc., Woodstock, UK), DISETRONIC™ pen(Disetronic Medical Systems, Bergdorf, Switzerland), HUMALOG MIX 75/25™pen, HUMALOG™ pen, HUMALIN 70/30™ pen (Eli Lilly and Co., Indianapolis,Ind.), NOVOPEN™ I, II and III (Novo Nordisk, Copenhagen, Denmark),NOVOPEN JUNIOR™ (Novo Nordisk, Copenhagen, Denmark), BD™ pen (BectonDickinson, Franklin Lakes, N.J.), OPTIPEN™, OPTIPEN PRO™, OPTIPENSTARLET™, and OPTICLIK™ (sanofi-aventis, Frankfurt, Germany), to nameonly a few. Examples of disposable pen delivery devices havingapplications in subcutaneous delivery of a pharmaceutical composition ofthe present invention include, but are not limited to the SOLOSTAR™ pen(sanofi-aventis), the FLEXPEN™ (Novo Nordisk), and the KWIKPEN™ (EliLilly), the SURECLICK™ Autoinjector (Amgen, Thousand Oaks, Calif.), thePENLET™ (Haselmeier, Stuttgart, Germany), the EPIPEN (Dey, L.P.), andthe HUMIRA™ Pen (Abbott Labs, Abbott Park Ill.), to name only a few.

In certain situations, the pharmaceutical composition can be deliveredin a controlled release system. In one embodiment, a pump may be used(see Langer, supra; Sefton, 1987, CRC Crit. Ref. Biomed. Eng. 14:201).In another embodiment, polymeric materials can be used; see, MedicalApplications of Controlled Release, Langer and Wise (eds.), 1974, CRCPres., Boca Raton, Fla. In yet another embodiment, a controlled releasesystem can be placed in proximity of the composition's target, thusrequiring only a fraction of the systemic dose (see, e.g., Goodson,1984, in Medical Applications of Controlled Release, supra, vol. 2, pp.115-138). Other controlled release systems are discussed in the reviewby Langer, 1990, Science 249:1527-1533.

The injectable preparations may include dosage forms for intravenous,subcutaneous, intracutaneous and intramuscular injections, dripinfusions, etc. These injectable preparations may be prepared by methodspublicly known. For example, the injectable preparations may beprepared, e.g., by dissolving, suspending or emulsifying the antibody orits salt described above in a sterile aqueous medium or an oily mediumconventionally used for injections. As the aqueous medium forinjections, there are, for example, physiological saline, an isotonicsolution containing glucose and other auxiliary agents, etc., which maybe used in combination with an appropriate solubilizing agent such as analcohol (e.g., ethanol), a polyalcohol (e.g., propylene glycol,polyethylene glycol), a nonionic surfactant [e.g., polysorbate 80,HCO-50 (polyoxyethylene (50 mol) adduct of hydrogenated castor oil)],etc. As the oily medium, there are employed, e.g., sesame oil, soybeanoil, etc., which may be used in combination with a solubilizing agentsuch as benzyl benzoate, benzyl alcohol, etc. The injection thusprepared is preferably filled in an appropriate ampoule.

Advantageously, the pharmaceutical compositions for oral or parenteraluse described above are prepared into dosage forms in a unit dose suitedto fit a dose of the active ingredients. Such dosage forms in a unitdose include, for example, tablets, pills, capsules, injections(ampoules), suppositories, etc. The amount of the aforesaid antibodycontained is generally about 5 to about 500 mg per dosage form in a unitdose; especially in the form of injection, it is preferred that theaforesaid antibody is contained in about 5 to about 100 mg and in about10 to about 250 mg for the other dosage forms.

Therapeutic Uses of the Antibodies

The present invention includes methods comprising administering to asubject in need thereof a therapeutic composition comprising ananti-GITR antibody (e.g., an anti-GITR antibody comprising any of theHCVR/LCVR or CDR sequences as set forth in Table 1 herein). Thetherapeutic composition can comprise any of the anti-GITR antibodies,antigen-binding fragments thereof, or ADCs disclosed herein, and apharmaceutically acceptable carrier or diluent.

The antibodies of the invention are useful, inter alia, for thetreatment, prevention and/or amelioration of any disease or disorderassociated with or mediated by GITR expression or activity, or treatableby blocking the interaction between GITR and GITRL, and/or inhibiting orstimulating GITR activity and/or signaling. For example, the antibodiesand antigen-binding fragments of the present disclosure can be used totreat immune and proliferative diseases or disorders, e.g., cancer, bymodulating the immune response, though, e.g., GITR activation.

The antibodies and antigen-binding fragments of the instant disclosurecan be used to treat a disease or disorder by enhancing an immuneresponse. The instant disclosure includes methods of modulatinganti-tumor immune response in a subject comprising administering to thesubject an anti-GITR antibody or antigen-binding fragment describedherein. In certain embodiments, the antibody or antigen-binding fragmentreduces the suppressive activity of T effector cells by T regulatorycells. In some embodiments, the antibody or antigen-binding fragment ofthe instant disclosure enhances intra-tumoral T effector/T regulatorycell ratio conducive for therapeutic benefit. In some embodiments, theantibody or antigen-binding fragment of the instant disclosure promotesT cell survival.

Exemplary diseases or disorders that can be treated by the antibodiesand antigen-binding fragments include immune and proliferative diseasesor disorders, e.g., cancer. The antibodies and antigen-binding fragmentsof the present invention can be used to treat primary and/or metastatictumors arising in the brain and meninges, oropharynx, lung and bronchialtree, gastrointestinal tract, male and female reproductive tract,muscle, bone, skin and appendages, connective tissue, spleen, immunesystem, blood forming cells and bone marrow, liver and urinary tract,and special sensory organs such as the eye. In some embodiments, theantibodies and antigen-binding fragments of the instant disclosure areused to treat solid or blood-borne tumors. In certain embodiments, theantibodies of the instant disclosure are used to treat one or more ofthe following cancers: renal cell carcinoma, pancreatic carcinoma, headand neck cancer, prostate cancer, malignant gliomas, osteosarcoma,colorectal cancer, gastric cancer (e.g., gastric cancer with METamplification), malignant mesothelioma, multiple myeloma, ovariancancer, cervical cancer, small cell lung cancer, non-small cell lungcancer, synovial sarcoma, thyroid cancer, breast cancer, melanoma,testicular, kidney, esophageal cancer, uterine cancer, endometrialcancer, or liver cancer.

In certain embodiments, the antibodies of the invention are useful fortreating an autoimmune disease, including but not limited to, alopeciaareata, autoimmune hepatitis, celiac disease, Graves' disease,Guillain-Barre syndrome, Hashimoto's disease, hemolytic anemia,inflammatory bowel disease, inflammatory myopathies, multiple sclerosis,primary biliary cirrhosis, psoriasis, rheumatoid arthritis, scleroderma,Sjögren's syndrome, systemic lupus erthyematosus, vitiligo, autoimmunepancreatitis, autoimmune urticaria, autoimmune thrombocytopenic purpura,Crohn's disease, diabetes type I, eosinophilic fasciitis, eosinophilicenterogastritis, Goodpasture's syndrome, myasthenia gravis, psoriaticarthritis, rheumatic fever, ulcerative colitis, vasculitis and Wegener'sgranulomatosis.

In the context of the methods of treatment described herein, theanti-GITR antibody may be administered as a monotherapy (i.e., as theonly therapeutic agent) or in combination with one or more additionaltherapeutic agents (examples of which are described elsewhere herein).

Combination Therapies and Formulations

Provided herein are also combination therapies utilizing an anti-GITRantibody of the present disclosure and any additional therapeutic agentthat may be advantageously combined with an antibody of the instantdisclosure or antigen-binding fragment thereof.

The present invention includes compositions and therapeutic formulationscomprising any of the anti-GITR antibodies described herein incombination with one or more additional therapeutically activecomponents, and methods of treatment comprising administering suchcombinations to subjects in need thereof.

The antibodies of the present invention may be combined synergisticallywith one or more anti-cancer drugs or therapy used to treat cancer,including, for example, renal cell carcinoma, colorectal cancer,glioblastoma multiforme, squamous cell carcinoma of head and neck,non-small-cell lung cancer, colon cancer, ovarian cancer,adenocarcinoma, prostate cancer, glioma, and melanoma. It iscontemplated herein to use anti-GITR antibodies of the invention incombination with immunostimulatory and/or immunosupportive therapies toinhibit tumor growth, and/or enhance survival of cancer patients. Theimmunostimulatory therapies include direct immunostimulatory therapiesto augment immune cell activity by either “releasing the brake” onsuppressed immune cells or “stepping on the gas” to activate an immuneresponse. Examples include targeting other checkpoint receptors,vaccination and adjuvants. The immunosupportive modalities may increaseantigenicity of the tumor by promoting immunogenic cell death,inflammation or have other indirect effects that promote an anti-tumorimmune response. Examples include radiation, chemotherapy,anti-angiogenic agents, and surgery.

The instant disclosure includes methods of modulating anti-tumor immuneresponse in a subject comprising administering to the subject ananti-GITR antibody in combination with one or more agonistic antibodiesagainst activating receptors and one or more blocking antibodies againstinhibitory receptors that enhance T-cell stimulation to promote tumordestruction.

The instant disclosure includes methods of modulating anti-tumor immuneresponse in a subject comprising administering to the subject ananti-GITR antibody or antigen-binding fragment described herein incombination with one or more isolated antibody or antigen-bindingfragment thereof that binds to a second T-cell activating receptor(i.e., other than GITR). In some embodiments, the second T-cellactivating receptor is CD28, OX40, CD137, CD27, or VEM. The instantdisclosure also includes formulations comprising an anti-GITR antibodyor antigen binding fragment thereof provided herein and an antibody orantigen-binding fragment that binds said second T-cell activatingreceptor.

In various embodiments, one or more antibodies of the present inventionmay be used in combination with an antibody to PD-L1, an antibody toPD-1 (e.g., nivolumab), a LAG-3 inhibitor, a CTLA-4 inhibitor (e.g.,ipilimumab), a TIM3 inhibitor, a BTLA inhibitor, a TIGIT inhibitor, aCD47 inhibitor, an antagonist of another T-cell co-inhibitor or ligand(e.g., an antibody to CD-28, 2B4, LY108, LAIR1, ICOS, CD160 or VISTA),an indoleamine-2,3-dioxygenase (IDO) inhibitor, a vascular endothelialgrowth factor (VEGF) antagonist [e.g., a “VEGF-Trap” such as afliberceptor other VEGF-inhibiting fusion protein as set forth in U.S. Pat. No.7,087,411, or an anti-VEGF antibody or antigen binding fragment thereof(e.g., bevacizumab, or ranibizumab) or a small molecule kinase inhibitorof VEGF receptor (e.g., sunitinib, sorafenib, or pazopanib)], an Ang2inhibitor (e.g., nesvacumab), a transforming growth factor beta (TGFβ)inhibitor, an epidermal growth factor receptor (EGFR) inhibitor (e.g.,erlotinib, cetuximab), an agonist to a co-stimulatory receptor (e.g., anagonist to glucocorticoid-induced TNFR-related protein), an antibody toa tumor-specific antigen (e.g., CA9, CA125, melanoma-associated antigen3 (MAGE3), carcinoembryonic antigen (CEA), vimentin, tumor-M2-PK,prostate-specific antigen (PSA), mucin-1, MART-1, and CA19-9), a vaccine(e.g., Bacillus Calmette-Guerin, a cancer vaccine), an adjuvant toincrease antigen presentation (e.g., granulocyte-macrophagecolony-stimulating factor), a bispecific antibody (e.g., CD3×CD20bispecific antibody, PSMA×CD3 bispecific antibody), a cytotoxin, achemotherapeutic agent (e.g., dacarbazine, temozolomide,cyclophosphamide, docetaxel, doxorubicin, daunorubicin, cisplatin,carboplatin, gemcitabine, methotrexate, mitoxantrone, oxaliplatin,paclitaxel, and vincristine), cyclophosphamide, radiotherapy, an IL-6Rinhibitor (e.g., sarilumab), an IL-4R inhibitor (e.g., dupilumab), anIL-10 inhibitor, a cytokine such as IL-2, IL-7, IL-21, and IL-15, anantibody-drug conjugate (ADC) (e.g., anti-CD19-DM4 ADC, and anti-DS6-DM4ADC), an anti-inflammatory drug (e.g., corticosteroids, andnon-steroidal anti-inflammatory drugs), a dietary supplement such asanti-oxidants or any palliative care to treat cancer. In certainembodiments, the anti-GITR antibodies of the present invention may beused in combination with cancer vaccines including dendritic cellvaccines, oncolytic viruses, tumor cell vaccines, etc. to augment theanti-tumor response. Examples of cancer vaccines that can be used incombination with anti-GITR antibodies of the present invention includeMAGE3 vaccine for melanoma and bladder cancer, MUC1 vaccine for breastcancer, EGFRv3 (e.g., Rindopepimut) for brain cancer (includingglioblastoma multiforme), or ALVAC-CEA (for CEA+ cancers).

In some embodiments, one or more anti-GITR antibodies described hereinare administered in combination with one or more anti-PD1 antibodies,including but not limited to those described in U.S. Patent PublicationNo. 2015/0203579, which is incorporated herein by reference in itsentirety. In some embodiments, the anti-GITR antibody is H1H14536P2 orH2aM14536P2. In some embodiments, the anti-PD1 antibody is REGN 2810(also known as H4H7798N as disclosed in U.S. Patent Publication No.2015/0203579), pembrolizumab, or nivolumab.

In certain embodiments, the anti-GITR antibodies of the invention may beadministered in combination with radiation therapy in methods togenerate long-term durable anti-tumor responses and/or enhance survivalof patients with cancer. In some embodiments, the anti-GITR antibodiesof the invention may be administered prior to, concomitantly or afteradministering radiation therapy to a cancer patient. For example,radiation therapy may be administered in one or more doses to tumorlesions followed by administration of one or more doses of anti-GITRantibodies of the invention. In some embodiments, radiation therapy maybe administered locally to a tumor lesion to enhance the localimmunogenicity of a patient's tumor (adjuvinating radiation) and/or tokill tumor cells (ablative radiation) followed by systemicadministration of an anti-GITR antibody of the invention. For example,intracranial radiation may be administered to a patient with braincancer (e.g., glioblastoma multiforme) in combination with systemicadministration of an anti-GITR antibody of the invention. In certainembodiments, the anti-GITR antibodies of the invention may beadministered in combination with radiation therapy and achemotherapeutic agent (e.g., temozolomide) or a VEGF antagonist (e.g.,aflibercept).

In certain embodiments, the anti-GITR antibodies of the invention may beadministered in combination with one or more anti-viral drugs to treatchronic viral infection caused by LCMV, HIV, HPV, HBV or HCV. Examplesof anti-viral drugs include, but are not limited to, zidovudine,lamivudine, abacavir, ribavirin, lopinavir, efavirenz, cobicistat,tenofovir, rilpivirine and corticosteroids. In some embodiments, theanti-GITR antibodies of the invention may be administered in combinationwith a LAG3 inhibitor, a CTLA-4 inhibitor or any antagonist of anotherT-cell co-inhibitor to treat chronic viral infection.

In certain embodiments, the anti-GITR antibodies of the invention may becombined with an antibody to a Fc receptor on immune cells for thetreatment of an autoimmune disease. In one embodiment, an antibody orfragment thereof of the invention is administered in combination with anantibody or antigen-binding protein targeted to an antigen specific toautoimmune tissue. In certain embodiments, an antibody orantigen-binding fragment thereof of the invention is administered incombination with an antibody or antigen-binding protein targeted to aT-cell receptor or a B-cell receptor, including but not limited to, Fcα(e.g., CD89), Fc gamma (e.g., CD64, CD32, CD16a, and CD16b), CD19, etc.The antibodies of fragments thereof of the invention may be used incombination with any drug or therapy known in the art (e.g.,corticosteroids and other immunosuppressants) to treat an autoimmunedisease or disorder including, but not limited to alopecia areata,autoimmune hepatitis, celiac disease, Graves' disease, Guillain-Barresyndrome, Hashimoto's disease, hemolytic anemia, inflammatory boweldisease, inflammatory myopathies, multiple sclerosis, primary biliarycirrhosis, psoriasis, rheumatoid arthritis, scleroderma, Sjögren'ssyndrome, systemic lupus erthyematosus, vitiligo, autoimmunepancreatitis, autoimmune urticaria, autoimmune thrombocytopenic purpura,Crohn's disease, diabetes type I, eosinophilic fasciitis, eosinophilicenterogastritis, Goodpasture's syndrome, myasthenia gravis, psoriaticarthritis, rheumatic fever, ulcerative colitis, vasculitis and Wegener'sgranulomatosis.

The instant disclosure also includes methods of modulating anti-tumorimmune response in a subject comprising administering to the subject ananti-GITR antibody or antigen-binding fragment described herein incombination with one or more isolated antibody or antigen-bindingfragment thereof that binds to a T-cell inhibitory receptor. In someembodiments, the T-cell inhibitory receptor is CTLA-4, PD-1, TIM-3,BTLA, VISTA, or LAG-3. The instant disclosure also includes formulationscomprising an anti-GITR antibody or antigen-binding fragment thereofprovided herein and an antibody or antigen-binding fragment that bindssaid T-cell inhibitory receptor.

The instant disclosure also includes methods of treating cancer byadministering an antibody or antigen-binding fragment thereof orformulation described herein to a subject in conjunction with radiationor chemotherapy.

In some embodiments, the anti-GITR antibodies of the present inventionare co-formulated with and/or administered in combination with one ormore additional therapeutically active component(s) selected from thegroup consisting of: an EGFR antagonist (e.g., an anti-EGFR antibody[e.g., cetuximab or panitumumab] or small molecule inhibitor of EGFR[e.g., gefitinib or erlotinib]), an antagonist of another EGFR familymember such as Her2/ErbB2, ErbB3 or ErbB4 (e.g., anti-ErbB2 [e.g.,trastuzumab or T-DM1 {KADCYLA®}], anti-ErbB3 or anti-ErbB4 antibody orsmall molecule inhibitor of ErbB2, ErbB3 or ErbB4 activity), anantagonist of EGFRvIII (e.g., an antibody that specifically bindsEGFRvIII), a cMET anagonist (e.g., an anti-cMET antibody), an IGF1Rantagonist (e.g., an anti-IGF1R antibody), a B-raf inhibitor (e.g.,vemurafenib, sorafenib, GDC-0879, PLX-4720), a PDGFR-α inhibitor (e.g.,an anti-PDGFR-α antibody), a PDGFR-β inhibitor (e.g., an anti-PDGFR-βantibody or small molecule kinase inhibitor such as, e.g., imatinibmesylate or sunitinib malate), a PDGF ligand inhibitor (e.g.,anti-PDGF-A, -B, -C, or -D antibody, aptamer, siRNA, etc.), a VEGFantagonist (e.g., a VEGF-Trap such as aflibercept, see, e.g., U.S. Pat.No. 7,087,411 (also referred to herein as a “VEGF-inhibiting fusionprotein”), anti-VEGF antibody (e.g., bevacizumab), a small moleculekinase inhibitor of VEGF receptor (e.g., sunitinib, sorafenib orpazopanib)), a DLL4 antagonist (e.g., an anti-DLL4 antibody disclosed inUS 2009/0142354 such as REGN421), an Ang2 antagonist (e.g., an anti-Ang2antibody disclosed in US 2011/0027286 such as H1H685P), a FOLH1antagonist (e.g., an anti-FOLH1 antibody), a STEAP1 or STEAP2 antagonist(e.g., an anti-STEAP1 antibody or an anti-STEAP2 antibody), a TMPRSS2antagonist (e.g., an anti-TMPRSS2 antibody), a MSLN antagonist (e.g., ananti-MSLN antibody), a CA9 antagonist (e.g., an anti-CA9 antibody), auroplakin antagonist (e.g., an anti-uroplakin [e.g., anti-UPK3A]antibody), a MUC16 antagonist (e.g., an anti-MUC16 antibody), a Tnantigen antagonist (e.g., an anti-Tn antibody), a CLEC12A antagonist(e.g., an anti-CLEC12A antibody), a TNFRSF17 antagonist (e.g., ananti-TNFRSF17 antibody), a LGR5 antagonist (e.g., an anti-LGR5antibody), a monovalent CD20 antagonist (e.g., a monovalent anti-CD20antibody such as rituximab), etc. Other agents that may be beneficiallyadministered in combination with antibodies of the invention include,e.g., tamoxifen, aromatase inhibitors, and cytokine inhibitors,including small-molecule cytokine inhibitors and antibodies that bind tocytokines such as IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-9, IL-11,IL-12, IL-13, IL-17, IL-18, or to their respective receptors.

The present invention includes compositions and therapeutic formulationscomprising any of the anti-GITR antibodies described herein incombination with one or more chemotherapeutic agents. Examples ofchemotherapeutic agents include alkylating agents such as thiotepa andcyclosphosphamide (Cytoxan™); alkyl sulfonates such as busulfan,improsulfan and piposulfan; aziridines such as benzodopa, carboquone,meturedopa, and uredopa; ethylenimines and methylamelamines includingaltretamine, triethylenemelamine, trietylenephosphoramide,triethylenethiophosphaoramide and trimethylolomelamine; nitrogenmustards such as chlorambucil, chlornaphazine, cholophosphamide,estramustine, ifosfamide, mechlorethamine, mechlorethamine oxidehydrochloride, melphalan, novembichin, phenesterine, prednimustine,trofosfamide, uracil mustard; nitrosureas such as carmustine,chlorozotocin, fotemustine, lomustine, nimustine, ranimustine;antibiotics such as aclacinomysins, actinomycin, authramycin, azaserine,bleomycins, cactinomycin, calicheamicin, carabicin, carminomycin,carzinophilin, chromomycins, dactinomycin, daunorubicin, detorubicin,6-diazo-5-oxo-L-norleucine, doxorubicin, epirubicin, esorubicin,idarubicin, marcellomycin, mitomycins, mycophenolic acid, nogalamycin,olivomycins, peplomycin, potfiromycin, puromycin, quelamycin,rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex,zinostatin, zorubicin; anti-metabolites such as methotrexate and5-fluorouracil (5-FU); folic acid analogues such as denopterin,methotrexate, pteropterin, trimetrexate; purine analogs such asfludarabine, 6-mercaptopurine, thiamiprine, thioguanine; pyrimidineanalogs such as ancitabine, azacitidine, 6-azauridine, carmofur,cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine;androgens such as calusterone, dromostanolone propionate, epitiostanol,mepitiostane, testolactone; anti-adrenals such as aminoglutethimide,mitotane, trilostane; folic acid replenisher such as frolinic acid;aceglatone; aldophosphamide glycoside; aminolevulinic acid; amsacrine;bestrabucil; bisantrene; edatraxate; defofamine; demecolcine;diaziquone; elfornithine; elliptinium acetate; etoglucid; galliumnitrate; hydroxyurea; lentinan; lonidamine; mitoguazone; mitoxantrone;mopidamol; nitracrine; pentostatin; phenamet; pirarubicin; podophyllinicacid; 2-ethylhydrazide; procarbazine; PSK™; razoxane; sizofiran;spirogermanium; tenuazonic acid; triaziquone;2,2′,2″-trichlorotriethylamine; urethan; vindesine; dacarbazine;mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine;arabinoside (“Ara-C”); cyclophosphamide; thiotepa; taxanes, e.g.paclitaxel (Taxol™, Bristol-Myers Squibb Oncology, Princeton, N.J.) anddocetaxel (Taxotere™; Aventis Antony, France); chlorambucil;gemcitabine; 6-thioguanine; mercaptopurine; methotrexate; platinumanalogs such as cisplatin and carboplatin; vinblastine; platinum;etoposide (VP-16); ifosfamide; mitomycin C; mitoxantrone; vincristine;vinorelbine; navelbine; novantrone; teniposide; daunomycin; aminopterin;xeloda; ibandronate; CPT-11; topoisomerase inhibitor RFS 2000;difluoromethylornithine (DMFO); retinoic acid; esperamicins;capecitabine; and pharmaceutically acceptable salts, acids orderivatives of any of the above. Also included in this definition areanti-hormonal agents that act to regulate or inhibit hormone action ontumors such as anti-estrogens including for example tamoxifen,raloxifene, aromatase inhibiting 4(5)-imidazoles, 4-hydroxytamoxifen,trioxifene, keoxifene, LY 117018, onapristone, and toremifene(Fareston); and anti-androgens such as flutamide, nilutamide,bicalutamide, leuprolide, and goserelin; and pharmaceutically acceptablesalts, acids or derivatives of any of the above.

The anti-GITR antibodies of the invention may also be administeredand/or co-formulated in combination with antivirals, antibiotics,analgesics, corticosteroids, steroids, oxygen, antioxidants, COXinhibitors, cardioprotectants, metal chelators, IFN-gamma, and/orNSAIDs.

The additional therapeutically active component(s), e.g., any of theagents listed above or derivatives thereof, may be administered justprior to, concurrent with, or shortly after the administration of ananti-GITR antibody of the present invention; (for purposes of thepresent disclosure, such administration regimens are considered theadministration of an anti-GITR antibody “in combination with” anadditional therapeutically active component). The present inventionincludes pharmaceutical compositions in which an anti-GITR antibody ofthe present invention is co-formulated with one or more of theadditional therapeutically active component(s) as described elsewhereherein.

The additional therapeutically active component(s) may be administeredto a subject prior to administration of an anti-GITR antibody of thepresent invention. For example, a first component may be deemed to beadministered “prior to” a second component if the first component isadministered 1 week before, 72 hours before, 60 hours before, 48 hoursbefore, 36 hours before, 24 hours before, 12 hours before, 6 hoursbefore, 5 hours before, 4 hours before, 3 hours before, 2 hours before,1 hour before, 30 minutes before, 15 minutes before, 10 minutes before,5 minutes before, or less than 1 minute before administration of thesecond component. In other embodiments, the additional therapeuticallyactive component(s) may be administered to a subject afteradministration of an anti-GITR antibody of the present invention. Forexample, a first component may be deemed to be administered “after” asecond component if the first component is administered 1 minute after,5 minutes after, 10 minutes after, 15 minutes after, 30 minutes after, 1hour after, 2 hours after, 3 hours after, 4 hours after, 5 hours after,6 hours after, 12 hours after, 24 hours after, 36 hours after, 48 hoursafter, 60 hours after, 72 hours after administration of the secondcomponent. In yet other embodiments, the additional therapeuticallyactive component(s) may be administered to a subject concurrent withadministration of an anti-GITR antibody of the present invention.“Concurrent” administration, for purposes of the present invention,includes, e.g., administration of an anti-GITR antibody and anadditional therapeutically active component to a subject in a singledosage form (e.g., co-formulated), or in separate dosage formsadministered to the subject within about 30 minutes or less of eachother. If administered in separate dosage forms, each dosage form may beadministered via the same route (e.g., both the anti-GITR antibody andthe additional therapeutically active component may be administeredintravenously, subcutaneously, etc.); alternatively, each dosage formmay be administered via a different route (e.g., the anti-GITR antibodymay be administered intravenously, and the additional therapeuticallyactive component may be administered subcutaneously). In any event,administering the components in a single dosage from, in separate dosageforms by the same route, or in separate dosage forms by different routesare all considered “concurrent administration,” for purposes of thepresent disclosure. For purposes of the present disclosure,administration of an anti-GITR antibody “prior to”, “concurrent with,”or “after” (as those terms are defined herein above) administration ofan additional therapeutically active component is consideredadministration of an anti-GITR antibody “in combination with” anadditional therapeutically active component).

The present invention includes pharmaceutical compositions in which ananti-GITR antibody of the present invention is co-formulated with one ormore of the additional therapeutically active component(s) as describedelsewhere herein using a variety of dosage combinations.

In exemplary embodiments in which an anti-GITR antibody of the inventionis administered in combination with a VEGF antagonist (e.g., a VEGF trapsuch as aflibercept), including administration of co-formulationscomprising an anti-GITR antibody and a VEGF antagonist, the individualcomponents may be administered to a subject and/or co-formulated using avariety of dosage combinations. For example, the anti-GITR antibody maybe administered to a subject and/or contained in a co-formulation in anamount selected from the group consisting of 0.01 mg, 0.02 mg, 0.03 mg,0.04 mg, 0.05 mg, 0.1 mg, 0.2 mg, 0.3 mg, 0.4 mg, 0.5 mg, 0.6 mg, 0.7mg, 0.8 mg, 0.9 mg, 1.0 mg, 1.5 mg, 2.0 mg, 2.5 mg, 3.0 mg, 3.5 mg, 4.0mg, 4.5 mg, 5.0 mg, 6.0 mg, 7.0 mg, 8.0 mg, 9.0 mg, and 10.0 mg; and theVEGF antagonist (e.g., a VEGF trap such as aflibercept) may beadministered to the subject and/or contained in a co-formulation in anamount selected from the group consisting of 0.1 mg, 0.2 mg, 0.3 mg, 0.4mg, 0.5 mg, 0.6 mg, 0.7 mg, 0.8 mg, 0.9 mg, 1.0 mg, 1.1 mg, 1.2 mg, 1.3mg, 1.4 mg, 1.5 mg, 1.6 mg, 1.7 mg, 1.8 mg, 1.9 mg, 2.0 mg, 2.1 mg, 2.2mg, 2.3 mg, 2.4 mg, 2.5 mg, 2.6 mg, 2.7 mg, 2.8 mg, 2.9 mg and 3.0 mg.The combinations/co-formulations may be administered to a subjectaccording to any of the administration regimens disclosed elsewhereherein, including, e.g., twice a week, once every week, once every 2weeks, once every 3 weeks, once every month, once every 2 months, onceevery 3 months, once every 4 months, once every 5 months, once every 6months, etc.

Administration Regimens

According to certain embodiments of the present invention, multipledoses of an anti-GITR antibody (or a pharmaceutical compositioncomprising a combination of an anti-GITR antibody and any of theadditional therapeutically active agents mentioned herein) may beadministered to a subject over a defined time course. The methodsaccording to this aspect of the invention comprise sequentiallyadministering to a subject multiple doses of an anti-GITR antibody ofthe invention. As used herein, “sequentially administering” means thateach dose of anti-GITR antibody is administered to the subject at adifferent point in time, e.g., on different days separated by apredetermined interval (e.g., hours, days, weeks or months). The presentinvention includes methods which comprise sequentially administering tothe patient a single initial dose of an anti-GITR antibody, followed byone or more secondary doses of the anti-GITR antibody, and optionallyfollowed by one or more tertiary doses of the anti-GITR antibody.

The terms “initial dose,” “secondary doses,” and “tertiary doses,” referto the temporal sequence of administration of the anti-GITR antibody ofthe invention. Thus, the “initial dose” is the dose which isadministered at the beginning of the treatment regimen (also referred toas the “baseline dose”); the “secondary doses” are the doses which areadministered after the initial dose; and the “tertiary doses” are thedoses which are administered after the secondary doses. The initial,secondary, and tertiary doses may all contain the same amount ofanti-GITR antibody, but generally may differ from one another in termsof frequency of administration. In certain embodiments, however, theamount of anti-GITR antibody contained in the initial, secondary and/ortertiary doses varies from one another (e.g., adjusted up or down asappropriate) during the course of treatment. In certain embodiments, twoor more (e.g., 2, 3, 4, or 5) doses are administered at the beginning ofthe treatment regimen as “loading doses” followed by subsequent dosesthat are administered on a less frequent basis (e.g., “maintenancedoses”).

In certain exemplary embodiments of the present invention, eachsecondary and/or tertiary dose is administered 1 to 26 (e.g., 1, 1½, 2,2½, 3, 3½, 4, 4½, 5, 5½, 6, 6½, 7, 7½, 8, 8½, 9, 9½, 10, 10½, 11, 11½,12, 12½, 13, 13½, 14, 14½, 15, 15½, 16, 16½, 17, 17½, 18, 18½, 19, 19½,20, 20½, 21, 21½, 22, 22½, 23, 23½, 24, 24½, 25, 25½, 26, 26½, or more)weeks after the immediately preceding dose. The phrase “the immediatelypreceding dose,” as used herein, means, in a sequence of multipleadministrations, the dose of anti-GITR antibody which is administered toa patient prior to the administration of the very next dose in thesequence with no intervening doses.

The methods according to this aspect of the invention may compriseadministering to a patient any number of secondary and/or tertiary dosesof an anti-GITR antibody. For example, in certain embodiments, only asingle secondary dose is administered to the patient. In otherembodiments, two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) secondarydoses are administered to the patient. Likewise, in certain embodiments,only a single tertiary dose is administered to the patient. In otherembodiments, two or more (e.g., 2, 3, 4, 5, 6, 7, 8, or more) tertiarydoses are administered to the patient. The administration regimen may becarried out indefinitely over the lifetime of a particular subject, oruntil such treatment is no longer therapeutically needed oradvantageous.

In embodiments involving multiple secondary doses, each secondary dosemay be administered at the same frequency as the other secondary doses.For example, each secondary dose may be administered to the patient 1 to2 weeks or 1 to 2 months after the immediately preceding dose.Similarly, in embodiments involving multiple tertiary doses, eachtertiary dose may be administered at the same frequency as the othertertiary doses. For example, each tertiary dose may be administered tothe patient 2 to 12 weeks after the immediately preceding dose. Incertain embodiments of the invention, the frequency at which thesecondary and/or tertiary doses are administered to a patient can varyover the course of the treatment regimen. The frequency ofadministration may also be adjusted during the course of treatment by aphysician depending on the needs of the individual patient followingclinical examination.

The present invention includes administration regimens in which 2 to 6loading doses are administered to a patient at a first frequency (e.g.,once a week, once every two weeks, once every three weeks, once a month,once every two months, etc.), followed by administration of two or moremaintenance doses to the patient on a less frequent basis. For example,according to this aspect of the invention, if the loading doses areadministered at a frequency of once a month, then the maintenance dosesmay be administered to the patient once every six weeks, once every twomonths, once every three months, etc.

Diagnostic Uses of the Antibodies

The anti-GITR antibodies of the present invention may also be used todetect and/or measure GITR, or GITR-expressing cells in a sample, e.g.,for diagnostic purposes. For example, an anti-GITR antibody, or fragmentthereof, may be used to diagnose a condition or disease characterized byaberrant expression (e.g., over-expression, under-expression, lack ofexpression, etc.) of GITR. Exemplary diagnostic assays for GITR maycomprise, e.g., contacting a sample, obtained from a patient, with ananti-GITR antibody of the invention, wherein the anti-GITR antibody islabeled with a detectable label or reporter molecule. Alternatively, anunlabeled anti-GITR antibody can be used in diagnostic applications incombination with a secondary antibody which is itself detectablylabeled. The detectable label or reporter molecule can be aradioisotope, such as ³H, ¹⁴C, ³²p, ³⁵S, or ¹²⁵I; a fluorescent orchemiluminescent moiety such as fluorescein, or rhodamine; or an enzymesuch as alkaline phosphatase, beta-galactosidase, horseradishperoxidase, or luciferase. Specific exemplary assays that can be used todetect or measure GITR in a sample include enzyme-linked immunosorbentassay (ELISA), radioimmunoassay (RIA), immuno-PET (e.g., ⁸⁹Zr, ⁶⁴Cu,etc.), and fluorescence-activated cell sorting (FACS).

Samples that can be used in GITR diagnostic assays according to thepresent invention include any tissue or fluid sample obtainable from apatient which contains detectable quantities of GITR protein, orfragments thereof, under normal or pathological conditions. Generally,levels of GITR in a particular sample obtained from a healthy patient(e.g., a patient not afflicted with a disease or condition associatedwith abnormal GITR levels or activity) will be measured to initiallyestablish a baseline, or standard, level of GITR. This baseline level ofGITR can then be compared against the levels of GITR measured in samplesobtained from individuals suspected of having a GITR related disease orcondition.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the methods and compositions of the invention, and are notintended to limit the scope of what the inventors regard as theirinvention. Efforts have been made to ensure accuracy with respect tonumbers used (e.g., amounts, temperature, etc.) but some experimentalerrors and deviations should be accounted for. Unless indicatedotherwise, parts are parts by weight, molecular weight is averagemolecular weight, temperature is in degrees Centigrade, and pressure isat or near atmospheric.

Example 1. Generation of Anti-GITR Antibodies

Anti-GITR antibodies were obtained by immunizing a VELOCIMMUNE® mouse(i.e., an engineered mouse comprising DNA encoding human immunoglobulinheavy and kappa light chain variable regions) with an immunogencomprising a soluble dimeric ecto domain of human GITR. The antibodyimmune response was monitored by a GITR-specific immunoassay. Severalfully human anti-GITR antibodies were isolated directly fromantigen-positive B cells without fusion to myeloma cells, as describedin US 2007/0280945A1.

Certain biological properties of the exemplary anti-GITR antibodiesgenerated in accordance with the methods of this Example are describedin detail in the Examples set forth below.

Example 2. Heavy and Light Chain Variable Region Amino Acid and NucleicAcid Sequences

Table 1 sets forth the amino acid sequence identifiers of the heavy andlight chain variable regions and CDRs of selected anti-GITR antibodiesof the invention. The corresponding nucleic acid sequence identifiersare set forth in Table 2.

TABLE 1 Amino Acid Sequence Identifiers Antibody SEQ ID NOs: DesignationHCVR HCDR1 HCDR2 HCDR3 LCVR LCDR1 LCDR2 LCDR3 H1H14474P 2 4 6 8 10 12 1416 H1H14486P 18 20 22 24 26 28 30 32 H1H14491P 34 36 38 40 42 44 46 48H1H14493P 50 52 54 56 58 60 62 64 H1H14495P 66 68 70 72 74 76 78 80H1H14503P 82 84 86 88 90 92 94 96 H1H14512P 98 100 102 104 106 108 110112 H1H14520P 114 116 118 120 122 124 126 128 H1H14523P 130 132 134 136138 140 142 144 H1H14524P 146 148 150 152 154 156 158 160 H4H14469P 162164 166 168 170 172 174 176 H4H14470P 178 180 182 184 186 188 190 192H4H14475P 194 196 198 200 202 204 206 208 H4H14476P 210 212 214 216 218220 222 224 H4H14508P 226 228 230 232 234 236 238 240 H4H14516P 242 244246 248 250 252 254 256 H4H14521P 258 260 262 264 266 268 270 272H4H14525P 274 276 278 280 282 284 286 288 H4H14528P 290 292 294 296 298300 302 304 H4H14530P 306 308 310 312 314 316 318 320 H4H14531P2 322 324326 328 402 404 406 408 H4H14532P2 330 332 334 336 402 404 406 408H4H14536P2 338 340 342 344 402 404 406 408 H4H14539P2 346 348 350 352402 404 406 408 H4H14541P2 354 356 358 360 402 404 406 408 H4H15736P2362 364 366 368 402 404 406 408 H4H15740P2 370 372 374 376 402 404 406408 H4H15744P2 378 380 382 384 402 404 406 408 H4H15745P2 386 388 390392 402 404 406 408 H4H15753P2 394 396 398 400 402 404 406 408

TABLE 2 Nucleic Acid Sequence Identifiers Antibody SEQ ID NOs:Designation HCVR HCDR1 HCDR2 HCDR3 LCVR LCDR1 LCDR2 LCDR3 H1H14474P 1 35 7 9 11 13 15 H1H14486P 17 19 21 23 25 27 29 31 H1H14491P 33 35 37 3941 43 45 47 H1H14493P 49 51 53 55 57 59 61 63 H1H14495P 65 67 69 71 7375 77 79 H1H14503P 81 83 85 87 89 91 93 95 H1H14512P 97 99 101 103 105107 109 111 H1H14520P 113 115 117 119 121 123 125 127 H1H14523P 129 131133 135 137 139 141 143 H1H14524P 145 147 149 151 153 155 157 159H4H14469P 161 163 165 167 169 171 173 175 H4H14470P 177 179 181 183 185187 189 191 H4H14475P 193 195 197 199 201 203 205 207 H4H14476P 209 211213 215 217 219 221 223 H4H14508P 225 227 229 231 233 235 237 239H4H14516P 241 243 245 247 249 251 253 255 H4H14521P 257 259 261 263 265267 269 271 H4H14525P 273 275 277 279 281 283 285 287 H4H14528P 289 291293 295 297 299 301 303 H4H14530P 305 307 309 311 313 315 317 319H4H14531P2 321 323 325 327 401 403 405 407 H4H14532P2 329 331 333 335401 403 405 407 H4H14536P2 337 339 341 343 401 403 405 407 H4H14539P2345 347 349 351 401 403 405 407 H4H14541P2 353 355 357 359 401 403 405407 H4H15736P2 361 363 365 367 401 403 405 407 H4H15740P2 369 371 373375 401 403 405 407 H4H15744P2 377 379 381 383 401 403 405 407H4H15745P2 385 387 389 391 401 403 405 407 H4H15753P2 393 395 397 399401 403 405 407

Antibodies are typically referred to herein according to the followingnomenclature: Fc prefix (e.g. “H1H,” “H4H,” etc.), followed by anumerical identifier (e.g. “14493,” “14495,” etc.), followed by a “P” or“P2” suffix, as shown in Tables 1 and 2. Thus, according to thisnomenclature, an antibody may be referred to herein as, e.g.,“H1H14486P,” “H4H14531 P2,” etc. The H1H, and H4H prefixes on theantibody designations used herein indicate the particular Fc regionisotype of the antibody. For example, an “H1H” antibody has a human IgG1Fc, an “H4H” antibody has a human IgG4 Fc, and an H2M has a mouse IgG2Fc (all variable regions are fully human as denoted by the first ‘H’ inthe antibody designation). As will be appreciated by a person ofordinary skill in the art, an antibody having a particular Fc isotypecan be converted to an antibody with a different Fc isotype, but in anyevent, the variable domains (including the CDRs)—which are indicated bythe numerical identifiers shown in Tables 1 and 2—will remain the same,and the binding properties are expected to be identical or substantiallysimilar regardless of the nature of the Fc domain.

Control Constructs Used in the Following Examples

Control constructs were included in the following experiments forcomparative purposes: Anti-GITR Control Ab I: a mouse anti-human GITRhybridoma with variable heavy and light chain domains having the aminoacid sequences of the corresponding domains of “clone 6C8” as set forthin WO 2006/105021 A2; produced with mIgG1 and mIgG2a constant regions inthe following examples; and Anti-GITR Control Ab II: a human anti-GITRantibody with variable heavy and light chain domains having the aminoacid sequences of the corresponding domains of “36E5” as set forth inU.S. Pat. No. 8,709,424 B2.

Example 3. Surface Plasmon Resonance Derived Binding Affinities andKinetic Constants of Human Monoclonal Anti-TNFRSF18 (GITR) Antibodies

Binding affinities and kinetic constants of human anti-GITR antibodieswere determined by surface plasmon resonance (Biacore 4000 or T-200) at37° C. (Table 3). Antibodies, expressed as human IgG1 or IgG4 (i.e.,“H1H” or “H4H” designations), were captured onto a mouse anti-human FcCM5 Biacore sensor surface (mAb-capture format) and soluble monomeric(human (h) GITR.mmh; SEQ ID NO: 409 and Macaca fasicularis (mf)GITR.mmh; SEQ ID NO: 412) or dimeric (hGITR.hFc; SEQ ID NO: 411 andhGITRmFc; SEQ ID NO: 410). GITR proteins were injected over the sensorsurface at a flow rate of 30 μL/minute. All Biacore binding studies wereperformed in a buffer composed of 0.01M HEPES pH 7.4, 0.15M NaCl, 3 mMEDTA, 0.05% v/v Surfactant P20 (HBS-ET running buffer). Antibody-reagentassociation was monitored for 4 minutes while dissociation in HBS-ETrunning buffer (10 mM HEPES, 150 mM NaCl, 3 mM EDTA, 0.05% (v/v)Surfactant P20, pH 7.4) was monitored for 10 minutes. Kineticassociation (k_(a)) and dissociation (k_(d)) rate constants weredetermined by fitting the real-time sensorgrams to a 1:1 binding modelusing Scrubber 2.0c curve fitting software. Binding dissociationequilibrium constants (K_(D)) and dissociative half-lives (t½) werecalculated from the kinetic rate constants as: K_(D) [M]=k_(d)/k_(a);and t_(1/2) (min)=(ln 2/(60*k_(d)). Results are summarized in Table 3.

TABLE 3 Biacore Binding Affinities of Human Fc mAbs at 37° C. Binding at37° C./Antibody Capture Format Antibody Analyte ka (Ms⁻¹) Kd (s⁻¹) K_(D)(Molar) t½ (min) H1H14503P hGITR.mmh 5.32E+05 7.39E−04 1.39E−09 15.6hGITR.mFc 1.12E+06 1.54E−04 1.37E−10 75.0 mfGITR.mmh 2.68E+05 5.60E−032.09E−08 2.1 H1H14474P hGITR.mmh 5.91E+05 1.16E−03 1.96E−09 9.9hGITR.mFc 1.21E+06 1.30E−04 1.07E−10 89.2 mfGITR.mmh 3.39E+05 9.51E−032.80E−08 1.2 H1H14495P hGITR.mmh 5.17E+05 1.27E−03 2.45E−09 9.1hGITR.mFc 1.14E+06 1.10E−04 9.68E−11 105.0 mfGITR.mmh 2.96E+05 7.23E−032.45E−08 1.6 H1H14486P hGITR.mmh 4.39E+05 1.23E−03 2.79E−09 9.4hGITR.mFc 9.65E+05 1.53E−04 1.59E−10 75.5 mfGITR.mmh 1.37E+05 1.66E−021.22E−07 0.7 H1H14524P hGITR.mmh 4.05E+05 1.47E−03 3.62E−09 7.9hGITR.mFc 9.22E+05 1.35E−04 1.46E−10 85.6 mfGITR.mmh 1.20E+05 1.89E−021.58E−07 0.6 H4H14530P hGITR.mmh 2.72E+05 1.38E−03 5.06E−09 8.4hGITR.mFc 2.93E+05 1.85E−04 6.30E−10 62.6 mfGITR.mmh 2.40E+05 6.11E−042.55E−09 18.9 H1H14491P hGITR.mmh 3.19E+05 1.62E−03 5.06E−09 7.2hGITR.mFc 8.42E+05 1.69E−04 2.01E−10 68.3 mfGITR.mmh 1.18E+05 8.89E−037.53E−08 1.3 H1H14523P hGITR.mmh 2.16E+05 1.86E−03 8.63E−09 6.2hGITR.mFc 5.55E+05 1.20E−04 2.16E−10 96.3 mfGITR.mmh 1.23E+05 1.09E−028.85E−08 1.1 H1H14493P hGITR.mmh 1.86E+05 2.50E−03 1.34E−08 4.6hGITR.mFc 5.24E+05 1.91E−04 3.65E−10 60.4 mfGITR.mmh 1.00E+04 1.40E−021.40E−06 0.8 H4H14532P2 hGITR.mmh 3.48E+05 6.45E−03 1.85E−08 1.8hGITR.mFc 7.20E+05 2.69E−04 3.73E−10 42.9 mfGITR.mmh 2.60E+05 6.48E−032.49E−08 1.8 H4H14521P hGITR.mmh 3.45E+05 7.84E−03 2.27E−08 1.5hGITR.mFc 1.23E+06 4.79E−04 3.89E−10 24.1 mfGITR.mmh 1.66E+05 3.34E−032.01E−08 3.5 H4H14536P2 hGITR.mmh 4.24E+05 9.76E−03 2.30E−08 1.2hGITR.mFc 1.26E+06 2.19E−04 1.73E−10 52.7 mfGITR.mmh 1.04E+05 1.47E−021.42E−07 0.8 H4H14476P hGITR.mmh 3.92E+05 1.23E−02 3.14E−08 0.9hGITR.mFc 9.06E+05 2.69E−04 2.97E−10 42.9 mfGITR.mmh 1.91E+05 1.07E−025.58E−08 1.1 H4H14516P hGITR.mmh 2.25E+05 7.38E−03 3.27E−08 1.6hGITR.mFc 1.68E+06 1.81E−03 1.08E−09 6.4 mfGITR.mmh 1.90E+05 1.12E−025.87E−08 1.0 H4H14508P hGITR.mmh 2.55E+05 9.35E−03 3.66E−08 1.2hGITR.mFc 1.21E+06 7.19E−04 5.97E−10 16.1 mfGITR.mmh 1.29E+05 5.07E−033.93E−08 2.3 H4H14469P hGITR.mmh 2.84E+05 1.22E−02 4.30E−08 0.9hGITR.mFc 1.20E+06 4.01E−04 3.35E−10 28.8 mfGITR.mmh 5.91E+04 2.43E−034.11E−08 4.7 H4H14475P hGITR.mmh 3.07E+05 1.40E−02 4.57E−08 0.8hGITR.mFc 1.60E+06 1.35E−03 8.47E−10 8.5 mfGITR.mmh 1.83E+05 7.65E−034.17E−08 1.5 H4H14528P hGITR.mmh 1.02E+05 5.23E−03 5.13E−08 2.2hGITR.mFc 1.58E+06 1.77E−03 1.12E−09 6.5 mfGITR.mmh NB NB NB NBH4H14525P hGITR.mmh 3.17E+05 1.66E−02 5.24E−08 0.7 hGITR.mFc 7.91E+053.38E−04 4.27E−10 34.2 mfGITR.mmh 1.33E+05 2.05E−02 1.55E−07 0.6H1H14520P hGITR.mmh 2.66E+05 1.67E−02 6.30E−08 0.7 hGITR.mFc 1.09E+065.83E−04 5.37E−10 19.8 mfGITR.mmh 1.99E+05 1.71E−02 8.59E−08 0.7H4H14470P hGITR.mmh 2.21E+05 1.43E−02 6.47E−08 0.8 hGITR.mFc 9.04E+051.04E−03 1.15E−09 11.1 mfGITR.mmh NB NB NB NB H4H14539P2 hGITR.mmh2.14E+05 1.77E−02 8.25E−08 0.7 hGITR.mFc 8.53E+05 4.72E−04 5.54E−10 24.5mfGITR.mmh 7.23E+04 1.65E−03 2.28E−08 7.0 Anti-GITR hGITR.mmh 2.16E+052.63E−02 1.22E−07 0.4 Control Ab I- hGITR.hFc 3.82E+05 7.80E−03 2.04E−081.5 mIgG1 mfGITR.mmh 2.18E+05 4.64E−02 2.13E−07 0.2 Anti-GITR hGITR.mmh1.94E+05 9.67E−04 4.99E−09 11.9 Control Ab II- hGITR.mFc 1.83E+061.73E−03 9.48E−10 6.7 hIgG1 mfGITR.mmh 2.31E+05 8.63E−03 3.74E−08 1.3 NB= No binding observed under conditions used

As shown in Table 3, all the anti-GITR antibodies of this inventionbound to human GITR, with several antibodies displaying sub-nanomolaraffinities to dimeric human GITR protein. Additionally, a majority ofthe anti-GITR antibodies also displayed cross reactivity to cynomolgusGITR protein. Cross reactivity to rodent GITR proteins was not observed(data not shown).

Example 4. Anti-GITR Antibodies Bind Specifically and Potently to HumanGITR Expressing Cells

In this example, the ability of anti-GITR antibodies to bindspecifically to a human GITR-expressing cell line was determined usingelectrochemiluminescence (ECL) based detection.

Briefly, human embryonic kidney (HEK)-293-D9 cells were stablytransfected with human GITR (amino acids M1-V241, NCBI Accession#NP_004186.1, SEQ ID: 413) via Lipofectamine 2000-mediated methodology.Transfectants were selected for at least two weeks in complete growthmedia+G418.

For cell binding studies, approximately 1×10⁵ hGITR/HEK293-D9 orparental HEK293-D9 cells, which do not express human GITR, were seededonto 96-well carbon electrode plates (MULTI-ARRAY, MSD) for 1 h at 37°C. Nonspecific binding sites were blocked with 2% BSA (w/v)+PBS for 1 hat room temperature (RT). Next, serial dilutions of anti-GITRantibodies, ranging from 1.7 pM to 100 nM, were added to cells for 1 hat RT. Plates were then washed to remove unbound antibodies (AquaMax2000plate washer, MSD Analytical Technologies) and plate-bound antibodieswere detected with a SULFO-TAG™ conjugated anti-human kappa light chainIgG antibody (Jackson Immunoresearch) for 1 h at RT.

Following washes, luminescent signals were recorded with a SECTOR Imager6000 (MSD) instrument. Direct binding signals (relative light units,RLU) were analyzed as a function of the antibody concentration and datawere fitted with a sigmoidal (four-parameter logistic) dose-responsemodel using GraphPad Prism™ software. The EC₅₀ for bindinghGITR/HEK293-D9 cells, defined as the concentration of antibody at which50% of the maximal binding signal is detected, was determined toindicate binding potency of each antibody. The signal detected with 100nM antibody binding to the hGITR expressing cells versus parental cellswas recorded as an indication of intensity and specificity of GITRbinding. Results are summarized in Table 4.

As summarized in Table 4, most of the anti-GITR antibodies of thisinvention bound specifically to human GITR expressing cells versusparental HEK293 with EC₅₀s ranging from 210 pM to 85 nM. A majority ofthe antibodies bound to human GITR-expressing cells with sub-nanomolarEC₅₀ values. The isotype control antibody did not display binding tohGITR-expressing or parental cell lines.

TABLE 4 Anti-GITR antibody binding EC₅₀ and binding intensity at 100 nMon human GITR expressing cells Binding to Binding to Binding tohGITR/HEK293- HEK293-D9 hGITR/HEK293- D9 cells Cells D9 cells (at 100nM) (at 100 nM) EC50 Average Signal Average Signal Antibody (M) (RLU)(RLU) H1H14474P 2.80E−10 6230 680 H1H14486P 4.30E−10 5830 280 H1H14491P4.00E−10 6840 300 H1H14493P 3.00E−10 7220 790 H1H14495P 4.30E−10 6470340 H1H14503P 2.10E−10 5880 330 H1H14512P 2.50E−10 4620 180 H1H14520P2.40E−10 6450 1130 H1H14523P 4.00E−10 6350 530 H1H14524P 2.10E−10 5740500 H4H14469P 2.30E−10 5230 260 H4H14470P 1.40E−09 8390 1580 H4H14475P8.00E−09 7500 1580 H4H14476P 5.70E−10 8120 1770 H4H14508P 4.50E−10 6870580 H4H14516P 7.00E−10 10330 2560 H4H14521P 4.30E−10 10080 600 H4H14525P6.00E−10 8840 1490 H4H14528P 4.50E−10 7310 420 H4H14530P 8.50E−08 4200520 H4H14532P2 4.30E−10 5740 300 H4H14536P2 3.60E−10 8960 330 H4H14539P23.00E−10 4910 300 Anti-GITR 2.60E−10 13750 10240 Control Ab II- hIgG1Isotype NB 750 650 Control Ab- hIgG4

In summary, this example demonstrates that the anti-GITR antibodies ofthis invention display specific and potent binding to humanGITR-expressing cell lines.

Example 5. Anti-GITR Antibodies are Partial Blockers and PartialActivators in NF-κB/Luciferase Reporter Assay in the Presence or Absenceof Fc Gamma R Antibody Anchoring

In this example, the ability of anti-GITR antibodies to activate hGITRor block hGITR ligand (hGITRL)-mediated receptor stimulation in thepresence or absence of antibody anchoring to Fc gamma receptors (Fcgamma Rs) was assessed via Luciferase-based reporter assays.

Briefly, a Jurkat cell line with stable incorporation of hGITR andNF-κB-dependent luciferase reporter was engineered(hGITR/Jurkat/NF-κBLuc). The NF-κB Luciferase reporter was introducedinto Jurkat Cells using the Cignal Lenti Reporter system(SABiosciences). Lentiviruses expressing hGITR were generated inHEK293/T17 utilizing the Lenti-X Lentiviral Expression System(Clontech). Jurkat/NF-κB-Luc cells were transduced with thehGITR-expressing lentivirus via polybrene-mediated transduction andselected in 500 ug/ml G418 for 2 weeks. For antibody anchoring studies,HEK293 cells were transduced with the Fc gamma RI-expressing lentivirus,as described above.

First, the activation and blocking properties of anti-hGITR antibodiesin the absence of Fc gamma R anchoring (non-anchored bioassay format)was assessed. Approximately 4×10⁴ Jurkat/NF-κBLuc/hGITR cells wereseeded overnight (ON) in PDL coated 96 well plates in OptiMEM+0.5% FBS.

To determine antibody activation ability, cells were incubated for 6 hat 37° C. with serially diluted anti hGITR antibodies or hGITRL withconcentrations ranging from 0.5 pM to 100 nM. To assess antibodyblocking of hGITRL mediated receptor stimulation, cells werepre-incubated for 30 min with serially diluted anti hGITR antibodies(0.5 pM to 100 nM) followed by a constant dose of 10 nM hGITRL for 6 h.

Next, the activation and blocking properties of selected anti-hGITRantibodies in the presence of Fc gamma R anchoring (anchored bioassayformat) was determined. Similar to the above,2.5×10⁴Jurkat/NfκBLuc/hGITR cells were seeded in PDL coated 96 wellplates in complete growth media.

To assess antibody activation, cells were pre-incubated for 1 h at 37°C. with serially diluted anti-hGITR mAbs or hGITRL (0.5 pM to 100 nM).Then, 1×10⁴ hFc gamma R1/HEK293 cells were immediately added to thewells followed by a 6 h incubation. To assess blocking,hGITR/Jurkat/NfκBLuc cells were pre-incubated for 1 h with seriallydiluted anti-hGITR antibodies (0.5 pM to 100 nM). 1×10⁴ hFcγR1/HEK293cells were added to the wells followed by the addition of a constantdose of 10 nM hGITRL.

For both anchored and non-anchored bioassay formats, Luciferase activitywas measured with One glow reagent (Promega) and relative light units(RLUs) were measured on a Victor luminometer (Perkin Elmer). TheEC₅₀/IC₅₀ values were determined from a four-parameter logistic equationover a 12-point response curve using GraphPad Prism. Results aresummarized in Table 5 and Table 6. To determine % blocking, backgroundRLU (relative light units) from untreated wells are subtracted fromtreated wells, and the percent blocking is calculated according to thefollowing formula: [100−(antibody RLU at max dose/constant ligand doseRLU)]*100]. % activation is calculated according the following formula:(normalized mAb RLU/max GITR ligand response)*100; normalized mAb RLU isdetermined by subtracting the RLU from untreated wells from treatedwells. Mean fold activation is calculated as: RLU at maximum Antibodydose/background RLU from untreated wells.

TABLE 5 Blocking and activation properties of anti-GITR antibodies inthe absence of Fc gamma R anchoring IC₅₀ % EC₅₀ % Antibody (nM)Blocking- (nM) Activation H4H14475P ND −2 1.0 70 H1H14491P 0.60 90 2.060 H4H14521P 3.80 60 0.4 50 H1H14503P 0.60 90 1.4 50 H4H14469P 0.70 902.3 50 H4H14516P 2.30 70 0.8 45 H1H14523P 0.90 70 2.5 40 H1H14524P 0.7080 2.2 40 H4H14528P 3.40 90 1.1 30 H1H14495P 0.70 80 1.3 30 H1H14474P0.80 80 1.2 30 H4H14508P 0.90 40 1.2 30 H4H14532P2 1.00 90 1.2 30H1H14486P 1.10 50 1.2 30 H1H14493P 0.60 90 1.2 25 H1H14512P 0.70 100 1.220 H4H14525P 1.40 70 1.1 20 H4H14539P2 1.20 30 1.3 20 H4H14536P2 2.00 901.1 20 H4H14470P 0.90 80 1.2 20 H4H14476P 2.60 90 1.0 10 H1H14520P 0.9080 1.1 10 Anti-GITR 0.10 54 1.02 25 Control Ab I- mIgG1 IsotypeNo-blocking NB (No-activating) NA Control- IgG1 (NB) NA Isotype NB NB NANA Control- IgG4

As summarized in the Table 5 above and Table 6 below, the antibodiestested displayed partial activating and partial-blocking properties inboth the non-anchored and anchored bioassay formats. In the non-anchoredformat, antibodies mediated receptor stimulation with EC₅₀s ranging from0.4 nM to 2.5 nM. Several antibodies, such as H4H14475P and H4H14491 Pwere potent activators of the GITR receptor displaying 70 and 60 percentactivation respectively. A majority of the antibodies tested alsodisplayed blocking of hGITRL mediated receptor stimulation, with IC₅₀sranging from 0.6 nM to 3.8 nM. Several exemplary antibodies, such asH1H14512P and H4H14536P2 displayed potent blocking activity of 100% and90% respectively. H4H14475P, the most potent activator, displayed theleast activity in the blocking assay (percent blocking: −2%).

TABLE 6 Blocking and activation properties of anti-GITR antibodies inthe presence of Fc gamma R anchoring IC₅₀ % EC₅₀ Fold ActivationAntibody (nM) Blocking (nM) over basal signal H1H14512P 0.10 64 0.02 7.0H4H14475P 0.20 43 0.04 8.0 H4H14536P2 0.20 73 0.01 5.0 Anti-GITR 0.20 600.10 6.0 Control Ab I- mIgG1 Anti-GITR 0.01 74 0.20 5.0 Control Ab I-mIgG2a Anti-GITR 0.20 70 0.01 8.0 Control Ab II- hIgG1

Selected antibodies tested in the Fc gamma R-anchoring bioassay formatalso displayed a range of activation and blocking properties. H4H14475P,the strongest activator in the non-anchored format also potentlyactivated hGITR in the anchored bioassay with a fold activation of 8.0above the basal signal. Strong blockers in the non-anchored blockingformat, such as H1H14512P and H4H14536P2, also displayed potent blockingin the anchored assay (% Blocking: 60% and 70%).

In summary, the results demonstrate that the anti-GITR antibodies ofthis invention display potent GITR activating properties as well as theability to block GITRL mediated receptor stimulation in the absence ofFc gamma R anchoring in an engineered bioassay. Exemplary antibodies,such as H4H14775P and H4H1536P2 also maintain their activating andblocking properties, respectively, in the presence of Fc gamma Ranchoring.

Example 6. Anti-GITR Antibody H4H14536P2 Demonstrates Potent Activity ina Naïve Human CD4+ T-Cell Proliferation Assay in the Presence andAbsence of Fc Gamma R Anchoring

As described above, anti-GITR antibodies were tested in an engineeredbioassay for their ability to activate hGITR in the presence or absenceof anchoring Fc gamma receptors (Fc gamma R). In this example, theeffect of antibody anchoring on hGITR activation was assessed in a navehuman CD4+ T-cell proliferation primary bioassay. The human CD4+ T-cellsystem has the advantage that GITR copy number is at endogenous levels,whereas the engineered system utilizes cells with a higher GITR copynumber.

First, anti-GITR antibodies were tested for CD4+ T-cell proliferativeability in the presence of plate-bound anti-CD3. Briefly, Human CD4+ Tcells were isolated from healthy donor leukopacks using Human CD4+ Tcell Enrichment Cocktail (Stemcell Technologies). Naïve T cells werefurther enriched by depletion of CD45RO+ cells by MACS (MiltenyiBiotech). Approximately 5×10⁴ T cells were plated onto 96-wellU-bottomed polystyrene plates pre-coated with a suboptimal amount of theanti-CD3 mAb OKT3 (30 ng/mL) and titrated amounts of anti-GITRantibodies or controls. Three days after stimulation, tritiatedthymidine (1 μCi per well, Perkin Elmer Health Sciences NET027001) wasadded to each microwell and pulsed for 18 hours. Cells were harvestedonto filter plates (Unifilter-96 GF/C 6005174) using a FiltermateHarvester (Perkin Elmer Health Sciences 0961962). Scintillation fluid(Perkin Elmer Health Sciences Microscint20 6013621) was added to filterplates and radioactive counts were measured using a plate reader (PerkinElmer Health Sciences Topcount NXT). T-cell proliferation relative tocontrol, given as the mean fold activation at 10.6 nM of antibodyconcentration, is presented in Table 7. In this assay format, 10.6 nMrepresented the point at which T-cell proliferation reached a plateau onthe dose response curve.

TABLE 7 T-cell proliferative activity (Fold activation) of plate-boundanti-GITR antibodies at 10.6 nM in the presence of plate-bound anti-CD3Ab Donor Mean Fold Antibody 1 2 3 4 5 6 7 8 Activation H4H14536P2 3 2424 25 24 47 26 16 23 H4H14508P 10 4 4 7 4 11 3 2 5 H4H14525P 6 1 1 2 1 32 1 2 H4H14469P 3 12 12 15 12 17 11 11 12 H4H14532P2 2 6 6 12 6 19 7 2 8H4H14470P 0 3 3 4 3 6 4 1 3 H4H14475P 0 2 2 2 2 12 1 0 3 H4H14528P 2 8 84 8 31 5 4 8 H4H14539P2 2 12 12 13 12 39 11 6 13 H4H14516P 1 4 4 12 4 144 1 5 H4H14521P 1 4 4 5 4 12 3 2 4 Anti-GITR 6 23 23 40 23 66 25 11 27Control Ab 1- mIgG1 Isotype 1 1 1 1 1 1 1 1 1 Control

As the results in Table 7 show, the anti-GITR antibodies testeddemonstrated T-cell proliferative ability when plate-bound in thepresence of plate-bound anti-CD3. The Anti-GITR Control Ab Idemonstrated proliferative activity 27-fold above the isotype control.The majority of the anti-GITR antibodies of this invention displayedactivation 2-8 fold above the isotype control, with several exemplaryantibodies, H4H14469P, H4H14539P2, and H4H14536P2 demonstratingactivation 12, 13 and 23 fold above the control, respectively. Insummary, the results demonstrate that the anti-GITR antibodies testeddemonstrate T-cell proliferative activity in this classical format.

Next, additional assay formats were employed to test the ability ofanti-GITR antibodies to activate T-cells in the presence or absence ofcell-surface bound Fc gamma R.

To assess anti-GITR antibody ability to activate T cells in the presenceof Fc gamma R1 anchoring, HEK293 cells were engineered to express thehigh affinity hFc gamma R1 receptor, as described above. HEK293/Fc gammaRI cells were treated with 50 ug/mL Mitomycin C for 30 min at 37° C. toinhibit proliferation. After subsequent washes to remove traces ofMitomycin C, cells were coated with 300 ng/mL anti-CD3 antibody OKT3 tostimulate T cell activation. HEK293/Fc gamma RI cells were co-culturedwith human naïve CD4+ T cells in a 1:2 ratio and titrated amounts ofanti-GITR antibodies or controls were added to the co-culture medium.

T cell proliferation was assessed by measurement of the levels oftritiated thymidine incorporation. 72 h after stimulation, tritiatedthymidine (0.5 μCi per well, Perkin Elmer Health Sciences) was added toeach microwell for an additional 18 h at 37° C. Cells were harvestedonto filter plates (Unifilter-96 GF/C 6005174) using a FiltermateHarvester (Perkin Elmer Health Sciences D961962). Scintillation fluid(Perkin Elmer Health Sciences Microscint20 6013621) was added to filterplates and radioactive counts were measured using a plate reader (PerkinElmer Health Sciences Topcount NXT). T-cell proliferation relative tocontrol, given as the mean fold activation at a 33 nM concentration ofantibody is presented in Table 8. In this assay format, 33 nMrepresented the point at which T-cell proliferation reached a plateau onthe dose response curve.

TABLE 8 T-cell proliferative activity (Fold activation) of anti-GITRantibodies at 33 nM in the presence of Fc gamma R anchoring Donor MeanFold Antibody 1 2 3 4 5 Activation H4H14536P2 1.3 6.3 1.5 2.7 15.7 5.5H4H14508P 1.0 0.7 1.1 1.8 1.3 1.2 H4H14525P 1.2 0.8 1.0 1.5 1.5 1.2H4H14469P 0.70 1.0 0.9 1.5 1.5 1.1 H4H14532P2 0.80 0.9 1.0 1.7 2.1 1.3H4H14470P 1.8 1.0 1.4 1.5 2.0 1.5 H4H14475P 1.0 1.3 1.3 1.6 1.5 1.3H4H14528P 0.9 1.5 1.1 1.9 1.7 1.4 H4H14539P2 0.9 0.7 1.1 1.5 1.5 1.1H4H14516P 1.2 0.9 1.2 1.3 1.1 1.1 H4H14521P 1.5 1.1 1.1 1.7 0.9 1.2H4H14476P 0.6 0.20 0.8 0.8 0.1 0.5 Anti-GITR Control mAbs ControlI-mIgG1 2.8 2.8 1.4 1.1 1.7 2.0 Control I-mIgG2a 1.1 0.1 1.0 1.0 1.2 1.3Control II-hIgG1 0.1 0.6 1.3 0.2 1.2 0.7 Isotype Control-hIgG4 1.0 1.01.0 1.0 1.0 1.0

TABLE 9 T-cell proliferative activity (EC₅₀) of anti-GITR antibodies at33 nM in the presence of Fc gamma R anchoring Donor Mean EC₅₀ Antibody 12 3 4 5 (nM) H4H14536P2 1.2 0.5 1.3 11.2 1.6 3.2 Control I-mIgG1 37.2 NA42.9 3.5 52.7 34.1

As the results in Table 8 summarize, several antibodies showedactivation above controls with levels ranging from 1-2 fold. However,one exemplary antibody, H4H14536P2, demonstrated potent T-cellproliferation activity in the anchored setting. With a mean foldactivation of 5.5, H4H14536P2 stimulated greater T-cell activationcompared to the anti-GITR comparator antibodies (mean fold activationrange: 0.7-2.0). H4H14536P2 had a mean EC₅₀ of T-cell proliferation of3.2 nM compared with 34.1 nM for the most potent anti-GITR control Ab,Control I-mIgG (Table 9). Furthermore, in this assay format, H4H14475P,a potent activator in the engineered bioassay described above,demonstrated modest proliferative activity in this primary bioassaysetting.

Next, antibodies were tested for T-cell proliferation activity in theabsence of Fc gamma R anchoring. Human CD4+ T cells were isolated asdescribed above, and plated onto 96-well U-bottomed polystyrene platespre-coated with 30 ng/mL of the anti-CD3 antibody, OKT3. Similar toabove, titrated concentrations of anti-GITR antibodies or controls wereadded to the culture medium. T cell proliferation was measured bytritiated thymidine incorporation. T-cell proliferation observed in fourdonors at 22 nM antibody concentration is presented as the foldactivation compared to isotype control in Table 10. The EC50 (nM) ofH4H14536P2 is shown in Table 11.

As observed in the anchored assay format, H4H14536P2 again displayedpotent T cell proliferative activity at 22 nM in the non-anchoredformat. H4H14536P2 activated T cells with a mean fold activation of 11.0and an EC₅₀ of 8.3 nM. In this assay format, control anti-GITR antibodyI exhibited no T-cell proliferation capability.

TABLE 10 T-cell proliferative activity (Fold activation) of anti-GITRantibodies at 22 nM in the absence of Fc gamma R anchoring Donor MeanFold Antibody 1 2 3 4 Activation H4H14536P2 6.2 4.2 10.1 23.4 11.0H4H14508P 0.7 0.9 0.9 1.4 1.0 H4H14525P 0.7 1.0 0.9 1.0 0.9 H4H14469P0.9 0.8 1.0 0.9 0.9 H4H14532P2 0.7 0.8 1.0 1.1 0.9 H4H14470P 0.7 0.9 1.01.7 1.1 H4H14475P 0.7 1.1 0.8 0.8 0.9 H4H14528P 0.6 0.8 0.9 1.0 0.8H4H14539P2 0.5 0.8 1.1 0.8 0.8 H4H14516P 0.7 1.2 1.0 0.9 0.9 H4H14521P0.5 1.2 0.8 1.0 0.9 H4H14476P 0.7 0.9 0.9 0.8 0.8 Anti-GITR Control AbControl I- mIgG1 0.7 0.8 1.0 1.0 0.9 Isotype Control 1.0 1.0 1.0 1.0 1.0

TABLE 11 EC50 (nM) of H4H14536P2 Donor: 1 2 3 4 Average H4H14536P2 EC₅₀(nM): 12.2 6.4 9.0 5.7 8.3

In summary, this example demonstrates that one exemplary anti-GITRantibody, H4H14536P2, displays potent T-cell proliferative activity inthe presence and absence of hFc gamma R1 anchoring, while the anti-GITRcomparative antibody Control I displayed no T-cell proliferativeactivity in the non-anchored setting. Thus, the ability of H4H14536P2 toactivate T cells in the absence of hFc gamma R1 anchoring is a uniqueproperty, implying that the antibody may not have to compete withendogenous IgG binding to Fc gamma receptors in vivo to retain activity.This unique property of H4H14536P2 may confer an advantage in atherapeutic setting.

Example 7. Administration of Anti-GITR Antibodies in Combination withAnti-PD1 Antibodies Synergistically Controls and Eradicates Tumors

As assessment of the effect of administering anti-GITR antibodies incombination with anti-PD1 antibodies on tumor growth was performed usingthe following methods. The results of the assessment are summarizedbelow.

Tumor Implantation, Treatment Regimen and Growth Measurement

MC38 colorectal cancer cells (obtained from ATCC) were implantedsubcutaneously in C57BL/6 mice (3×10⁵ cells/mouse) (defined as day 0).On day 6 (i.e., 6 days post tumor implantation), mice were segregatedinto 4 groups (5 mice per group) and each group was treatedintra-peritoneally (IP) with: (1) rat IgG2a (2A3, Bio X cell, Cat.#BE0089) (isotype control)+rat IgG2b (LTF2, Bio X cell, Cat. #BE0090)(isotype control) (2) anti-GITR monoclonal antibody DTA1 (rat anti-mouseGITR, Bio X cell, Cat. #BE0063)+rat IgG2a (control) (3) anti-PD-1monoclonal antibody RPM1-14 (rat anti-mouse PD-1, Bio X cell, Cat.#BE0146)+rat IgG2b (control) or (4) anti-GITR antibody DTA1+anti-PD-1antibody RPM1-14. Antibody injection(s) were then administrated again onday 13. Antibody treatments were dosed at 5 mg/kg of each antibody.Tumors were measured two dimensionally (length×width) and tumor volumewas calculated (length×width²×0.5). Mice were euthanized when the tumorreached a designated tumor end-point (tumor volume>2000 mm³ or tumorulceration).

Tumor Re-Challenge Assessment

Mice treated with the combination of anti-PD-1 antibody and anti-GITRantibody that remained tumor free for over 80 days were re-challengedwith 3×10⁵ of the syngeneic tumor (MC38) in the right flank and 2.5×10⁵of an allogeneic (B16F10.9) tumor cell line (melanoma cell line, ATCC)in the left flank. Tumors were monitored as described above.

Antibody Depletion Experiments

Mice injected with different depleting mAbs (anti-CD4, anti-CD8,anti-CD25,) starting at one day prior of tumor challenge and given attwice weekly for total eight doses, were treated with the combinationtherapy or the isotype control IgG. The depletion efficiency wasconfirmed by FACS analysis of peripheral blood samples.

Flow Cytometry (FACS) Analysis of Intratumoral Lymphocytes

Mice were treated as described above. Five days after antibodytreatment, tumor and spleen were collected. Tumors were minced withscissors and dissociated to single cell suspension with LiberaseTL/DNAse I mix. Spleens were dissociated with gentleMACS OctoDissociator. Cells were stained with panels of FACS antibodies againstmouse CD45, CD3, CD4, CD8, CD25 and FoxP3, as well as activation markers(PD1, GITR, Ki67, CD160, CTLA4, ICOS, TIM3, LAG3, KLRG1 and CD44). Cellswere acquired on BD Fortessa X20 or LSR II and analyzed by FlowJosoftware.

Administration of Anti-Mouse GITR Antibodies in Combination withAnti-Mouse PD1 Antibodies Significantly Induces Tumor Regression andProvides Long-Term Tumor Remission in MC38 Bearing Mice

Using the methods described above, the efficacy of administering ananti-mouse GITR antibody (clone DTA-1, Bio X cell, Cat. #BE0063) incombination with an anti-mouse PD-1 antibody (clone RMP1-14, Bio X cell,Cat. #BE0146) in the control of subcutaneous MC38 tumors was assessed.As shown in FIG. 1 and Tables 12 and 13, combination treatment of PD1blockade and anti-GITR (DTA-1) antibody significantly induced tumorregression in MC38 tumor bearing mice, in comparison to anti-PD-1 oranti-GITR mAb alone or isotype control treated mice. Furthermore, micetreated with combination therapy showed long-term tumor remission, as100% of the mice remained tumor free for over 120 days (FIG. 2 , Tables14, 15).

TABLE 12 Average tumor volumes for each treatment group (mm³ ± SEM) andtumor free mice following anti-GITR and/or anti-PD-1 Ab treatment TumorVolume (mm3) Tumor Mean (SEM) Free mice Treatment Group Day 10 Day 13Day 17 Day 19 Day 21 Day 21 Isotype (Rat IgG2a + 196 (44) 232 (46) 802(869) NA NA 0/5 Rat IgG2b) Anti-PD1 + Rat IgG2b 181 (37) 259 (103) 551(199) 880 (335) 1550 (616) 0/5 Anti-GITR + Rat IgG2a 172 (9) 262 (72)407 (112) 741 (269) 882 (307) 0/5 Anti-GITR + Anti-PD1 130 (29) 41 (13)0 (0) 0 (0) 0 (0) 5/5

TABLE 13 Summary of tumor free mice of three independent experimentsfollowing anti-GITR and/or anti-PD1 Ab treatment Tumor Free miceTreatment Group Day 21 Isotype (Rat IgG2a + Rat IgG2b) 0/15 Anti-PD1 +Rat IgG2b 0/15 Anti-GITR + Rat IgG2a 1/15 Anti-GITR + Anti-PD1 10/15 Administration of Anti-Mouse GITR Antibodies in Combination withAnti-Mouse PD1 Antibodies Induces Tumor/Antigen-Specific ImmunologicMemory Response

To determine whether mice treated with the combined administration ofanti-PD-1 and anti-GITR antibodies developed a tumor/antigen-specificmemory response, survival tumor-free mice were re-challenged with 3×10⁵of syngeneic MC38 colon carcinoma cells in the right flank and 2.5×10⁵of allogeneic melanoma cell line B16F10.9 in the left flank. It wasfound that MC38 tumors did not grow in mice treated with the anti-PD1antibody and anti-GITR antibody combination, while the same tumors grewin naive control mice (without any previous treatment) (FIG. 3 ). Incontrast, the allogeneic tumor (melanoma) did not grow in both groups,demonstrating that the combined administration of anti-PD-1 and antiGITR antibodies induced tumor-antigen specific immunologic memoryresponse capable of controlling the second challenge with the same typeof tumor.

TABLE 14 Survival Proportions (percentage) Anti-PD-1 + Days IsotypeAnti-PD-1 Anti-GITR Anti-GITR 0 100 100 100 100 17 80 21 40 24 0 60 2620 35 20 52 0 0 123 100

Immune Population Study

Mice were treated with CD4, CD8 and CD25 depleting mAbs prior toanti-PD-1 antibody and anti-GITR antibody combination treatment. It wasfound that depletion of CD8+ cells fully abrogated the anti-tumoraleffect (MC38 tumors), while depletion of CD4 or CD25 T cells showedpartial inhibition (FIG. 4 , Table 15). Thus, the anti-tumor effect ofthe combination therapy in MC38 tumors appears predominantly dependenton CD8+ T cells.

The effect of anti-GITR and anti-PD1 combination treatment on tumorinfiltrating lymphocytes (TILs) was assessed. It was found that thecombination treatment induced a significant increase in the CD8/Tregratio in comparison to mono-therapy treatment (anti-PD-1 or anti-GITR)or isotype control (FIG. 5 ). The effect of the combination treatment onCD4/Treg ratio was found to be less pronounced. Anti-PD-1 and anti-GITRcombination treatment decreased the percentage of intra-tumoral Tregswhile it increased the CD8 T cells (FIG. 6 ). Further, anti-PD-1treatment alone induced expansion of the Treg cell number, while theanti-PD-1/anti-GITR combination treatment significantly reduced it incomparison to the isotype control treated mice.

TABLE 15 Anti-tumor efficacy after CD4, CD8, or CD25 depletion Tumorsize (mm³) Depletion Mean (SEM) Immunotherapy Antibody Day 8 Day 12 Day16 Isotype control Isotype control 55 (12) 161 (60) 555 (224) Anti-CD448 (17) 60 (22) 135 (71) Anti-CD8 49 (17) 176 (431) 825 (431) Anti-CD2559 (16) 61 (21) 182 (68) Anti-GITR + Isotype control 43 (19) 26 (16) 11(7) Anti-PD1 Anti-CD4 68 (21) 50 (32) 123 (122) Anti-CD8 67 (23) 222(86) 1041 (543) Anti-CD25 14 (6) 35 (30) 80 (64)Administration of Anti-Human GITR Antibodies in Combination withAnti-Mouse PD1 Antibodies Significantly Induces Tumor Regression andProvides Long-Term Tumor Remission in MC38 Bearing GITR/GITRL HumanizedMice

The efficacy of administering an anti-human GITR antibody (H2aM14536P2)in combination with an anti-mouse PD-1 antibody (clone RMP1-14 Bio Xcell, Cat. #BE0146) in the control of subcutaneous MC38 tumors wasassessed in GITR/GITRL humanized mice. It was found that anti-mouse PD-1blockade synergized with the anti-human GITR antibody and significantlyinduced tumor regression (4/6 mice) in MC38 tumor bearing mice, incomparison to anti-PD1 (1/7) or anti-GITR (1/7) mAb alone or isotypecontrol (0/7) treated mice, as shown in the average tumor growth curves(FIG. 7 , Table 16). Further, mice treated with the combination therapyshowed long-term tumor remission, as over 60% of the mice remain tumorfree at day 50, in comparison to 0% for the isotype control and 10% forthe anti-PD-1 or the anti-GITR treatment groups (FIG. 8 , Table 16).

Anti-Human GITR Antibodies Increase Intra-Tumoral CD8/TreQ Ratio

The effect of anti-human GITR antibodies on intra-tumoral and splenic Tcell populations was assessed. Anti-human GITR antibodies H2aM14536P2and H1H14536P2 were evaluated. It was found that both anti-human GITRantibody isotypes (mlg2a and hlgG1) induced a significant increase inthe intra-tumoral CD8/Treg ratio (FIG. 9 ). The same treatment had noeffect on peripheral spleen T cell subsets. Human IgG1 and mouse IgG2aisotype IgG were used in the assay for controls.

TABLE 16 Anti-tumor efficacy mediated by anti-human GITR antibody andanti-mouse PD1 antibody treatment Tumor size (mm³) Tumor Free Mean (SEM)Mice Treatment Group Day 9 Day 13 Day 16 Day 19 Day 51 Isotype control146 (26) 248 (53) 402 (97) 838 (205) 0/7 (0%) Anti-mPD1 120 (23) 163(50) 275 (103) 617 (257) 1/7 (14%) H2aM14536P2 134 (28) 162 (51) 194(51) 346 (87) 1/7 (14%) H2aH14536P2 + 122 (18) 90 (54) 114 (88) 192(165) 4/6 (67%) Anti-PD-1

TABLE 17 Anti-tumor efficacy mediated by anti-mouse GITR + anti-humanPD1 Ab treatment Tumor size (mm3) Treatment Mean (SEM) Group Day 13 Day17 Day 20 Day 24 Isotype 301 (38) 742 (81) 1392 (104) 2790 (366) controlAnti-PD1 184 (21) 354 (143) 589 (201) 937 (324) (REGN2810) Anti-GITR 362(99) 713 (360) 1199 (563) NA Anti-GITR + 212 (117) 120 (60) 127 (62) 167(98) Anti-PD-1Administration of Anti-Mouse GITR Antibodies in Combination withAnti-Human PD1 Antibodies Significantly Induces Tumor Regression andProvides Long-Term Tumor Remission in MC38 Bearing PD1/PDL1 HumanizedMice

The efficacy of administering an anti-mouse GITR antibody (DTA-1) incombination with an anti-human PD-1 antibody (REGN2810, also known asH4H7798N as disclosed in US Patent Publication No. 2015/0203579) in thecontrol of subcutaneous MC38 tumors was assessed in PD1/PDL1 humanizedmice. It was found that anti-human PD-1 blockade synergized with theanti-mouse GITR antibody and induced tumor growth delay in MC38 tumorbearing mice, in comparison to anti PD1 or anti GITR mAb alone orisotype control treated mice as shown in the average tumor growth curves(FIG. 10 , Table 17). Further, mice treated with the combination therapyshowed long-term tumor remission as over 40% of the mice remained tumorfree at day 45, in comparison to 0% for the isotype control, theanti-PD-1 or the anti-GITR treatment groups (FIG. 11 ).

Example 8: RNA Extraction and Analysis Single-Cell Sorting RNA-SeqAnalysis

On day 8 and 11 post tumor challenge, single cell suspension of tumorwas prepared by mouse tumor dissociation kit (Miltenyi Biotec, BergischGladbach, DE) and spleens were dissociated with gentleMACS™ OctoDissociator (Miltenyi Biotec). Tumors and spleens from the sametreatment group were pooled and viable CD8+ T cells were sorted by FACS.FACS sorted T cells were mixed with C1 Cell Suspension Reagent(Fluidigm, South San Francisco, Calif.) before loading onto a 5- to10-μm C1 Integrated Fluidic Circuit (IFC; Fluidigm). LIVE/DEAD stainingsolution was prepared by adding 2.5 μL ethidium homodimer-1 and 0.625 μLcalcein AM (Life Technologies, Carlsbad, Calif.) to 1.25 mL C1 Cell WashBuffer (Fluidigm) and 20 μL was loaded onto the C1 IFC. Each capturesite was carefully examined under a Zeiss microscope in bright field,GFP, and Texas Red channels for cell doublets and viability. Celllysing, reverse transcription, and cDNA amplification were performed onthe C1 Single-Cell Auto Prep IFC, as specified by the manufacturer(protocol 100-7168 E1). The SMARTer™ Ultra Low RNA Kit (Clontech,Mountain View, Calif.) was used for cDNA synthesis from the singlecells. Illumina NGS libraries were constructed using the NEXTERA XT DNASample Prep kit (Illumina), according to the manufacturer'srecommendations (protocol 100-7168 E1). A total of 2,222 single cellswere sequenced on Illumina NextSeq (Illumina, San Diego, Calif.) bymultiplexed single-read run with 75 cycles. Raw sequence data (BCLfiles) were converted to FASTQ format via Illumina CASAVA 1.8.2. Readswere decoded based on their barcodes. Read quality was evaluated usingFastQC (www.bioinformatics.babraham.ac.uk/projects/fastqc/).

Example 9: Role of CD226 and TIGIT in Combination Treatment

Genetic inactivation or pharmacological inhibition of CD226 reversed thetumor regression mediated by anti-GITR/anti-PD1 combination treatment insome experiments, while inhibition of other TNF-receptor or B7superfamily members had no effect.

CD226 Blocking Experiment

0.5 mg of anti-CD226 (10E5, eBioscience, San Diego, Calif.) or rat IgG2bisotype control IgG (LTF2, Bio X Cell, West Lebanon, N.H.) were injectedintraperitoneally (i.p.) on day 5 post tumor challenge and one day priorto immunotherapy. Perpendicular tumor diameters were measured blindly2-3 times per weeks using digital calipers (VWR, Radnor, Pa.). Volumewas calculated using the formula L×W×0.5, where L is the longestdimension and W is the perpendicular dimension. Differences in survivalwere determined for each group by the Kaplan-Meier method and theoverall P value was calculated by the log-rank testing using survivalanalysis by PRISM version 6 (GraphPad Software Inc., La Jolla, Calif.).An event was defined as death when tumor burden reached theprotocol-specified size of 2000 mm³ in maximum tumor volume to minimizemorbidity.

As shown in FIGS. 12 and 13 , MC38 tumor bearing mice were treated witheither CD226 blocking Ab or isotype Ab (control IgG) 1d prior toimmunotherapy with anti-GITR+anti-PD-1 or isotype Abs. Average tumorgrowth curve (FIG. 12 ) and survival curves (FIG. 13 ) are shown. Dataare representative of three experiments, n=5 mice per group, survivalanalysis by Log-rank test.

Wild type or TIGIT KO mice were challenged with MC38 tumors, treatedwith anti-CD226 or control IgG and either received isotype control (FIG.14 ) or anti-GITR+anti-PD-1 combination therapy (FIG. 15 ). Data shownare average tumor growth curves representative of two experiments (n=4-5mice per group).

Using the CD226 blocking mAb, it was shown that co-stimulatory signalingthrough CD226 is required for the anti-tumor immunity mediated bycombination treatment. Furthermore, the CD226 signaling pathway wasrequired for enhanced tumor surveillance in TIGIT KO mice (FIGS. 14 and15 ).

RNA Signatures in CD8+ T Cells from Combination Treatment Samples

To identify unique gene signatures in clonally expanded CD8+ T cells(tumors harvested at day 11) from combination treatment samples,comprehensive comparisons across different treatment groups wereperformed. Genes upregulated in clonally expanded CD8+ T cells fromcombination therapy were compared to upregulated genes of CD8+ T cellsfrom isotype treatment or non-expanded CD8+ T cells with combinationtreatment. Heat mapping analysis identified thirty genes overlappingwithin the comparison. An RNA signature change of ≥2-fold (p<0.01) wasobserved within the expanded CD8 T cell population for the 30 genesafter the anti-GITR/anti-PD1 combination treatment of tumors. Those 30genes include Id2, S100a11, Ndufb3, Serinc3, Ctsd, S100a4, Ppp1ca, Lbr,Peli1, Lcp2, Ube2h, Cd226, Mapkapk3, Racgap1, Arf3, Mki67, Ergic2, Azi2,Dync1i2, Sik1, Pde4d, Ppp3cc, Nek7, Emc4, Vav1, Dock10, Tmem173, Fam3c,Ppp1cc, and Glud1.

A four-way comparison across all five groups (i.e., (i) isotypetreatment, (ii) anti-GITR expanded CD8, (iii) anti-GITR/anti-PD1combination expanded CD8, (iv) anti-PD1 expanded CD8, and (v)anti-GITR/anti-PD1 combination non-expanded CD8) was next performed toidentify genes specifically regulated upon combination therapy versusmonotherapy treatment. Two overlapping upregulated genes (p<0.01, ≥2fold change in expression) were identified in the four-way analysis.CD226, which is a costimulatory molecule that plays an important role inanti-tumor response, was identified as one of the two genes sharedacross different comparison pairs. Expression analysis of differentsubsets of intratumoral CD8+ T cells ((a) total, (b) clonally expanded,or (c) non-expanded) across treatment groups (i.e., (i) isotype, (ii)anti-GITR, (iii) anti-PD1, and (iv) anti-GITR/anti-PD1 combination)revealed that CD226 mRNA levels were significantly increased bycombination treatment on clonally expanded T cells (fold change=10.7),while this difference was diluted in bulk (fold change=3.5) andnon-expanded CD8⁺ T cells (not significant). Further, CD226 mRNA levelswere significantly increased by combination treatment on clonallyexpanded CD8 T cells in comparison to anti-PD-1 (fold change=6.5) andanti-GITR (fold change=9.2) (FIG. 16 ).

Association Between PD1 and CD226

The potential association between PD1 and CD226 molecules was nextinvestigated. To examine if CD226 is a target for desphosphorylation bythe PD1-Shp2 complex, we reconstituted different components involved inT cell signaling in a cell-free large unilamellar vesicle (LUV) system(i.e., CD3, CD226, cytosolic tyrosine kinase Lck, Zap70, SLP76 52, andPI3K (p85a). The sensitivity of each component in response to PD-1titration on the LUVs was measured by phosphotyrosine (pY)immunoblotting (FIG. 17 ). We confirmed that TCR/CD3ζ was not a targetof desphosphorylation by PD-1-Shp2, whereas CD226 was efficientlydephosphorylated by PD1-Shp2 in a dose dependent manner after 30 minutesof treatment (FIG. 17 ). This data demonstrated an association betweenPD-1 and CD226.

Next, the relationship between PD-1 inhibition and CD226 expression wasinvestigated in a clinical setting. RNA-seq analysis was performed ontumor biopsies collected from 43 advanced cancer patients pre- andpost-PD-1 targeted treatment. CD226 expression was significantlyincreased after two doses of anti-hPD-1 treatment in cancer patients(FIG. 22 ). Further, clinical data from The Cancer Genome Atlas (TCGA)was interrogated to examine if CD226 expression level correlates withthe overall T cell activation strength and may be predictive of a betterprognosis in cancer patients. Indeed, patients with high baseline CD226expression have significantly higher survival probabilities in five(skin cutaneous melanoma, lung adenocarcinoma, head and neck squamouscarcinoma, uterine corpus endometrial carcinoma and sarcoma) out oftwenty different types of cancer evaluated (skin cutaneous melanoma,lung adenocarcinoma, head and neck squamous carcinoma, uterine corpusendometrial carcinoma, sarcoma, rectum adenocarcinoma, breast invasivecarcinoma, kidney renal clear cell carcinoma, cervical squamous cellcarcinoma and endocervical adenocarcinoma, glioblastoma multiforme,colon adenocarcinoma, stomach adenocarcinoma, bladder urothelialcarcinoma, thyroid carcinoma, prostate adenocarcinoma, pancreaticadenocarcinoma, brain lower grade glioma, lung squamous cell carcinoma,kidney renal papillary cell carcinoma, and ovarian serouscystadenocarcinoma. Overall, these results support an immunotherapystrategy that boosts CD226 signaling while simultaneously blocking TIGIT(e.g., via anti-GITR treatment) for maximum T cell activation.

Genetic Inactivation of CD226

Using a CD226 blocking mAb, we showed that costimulatory signalingthrough CD226 was required for the anti-tumor immunity mediated bycombination treatment (FIGS. 12, 13 ). Since CD226 Ab could possiblyhave a potential depleting effect on subset of CD8 T cells, CD226 wasgenetically inactivated in C57BL/6 background mice to confirm thatresult. CD226−/− mice showed no defect on T cell (CD4+, CD8+, Tregs)homeostasis (FIG. 18 , panels A-D) and responded similarly to wild-typemice to TCR activation (FIG. 18 , panels E-I). We observed that thecombination treatment no longer conferred the anti-tumor effect orsurvival benefit in CD226−/− mice, suggesting that CD226 was essentialfor the observed anti-tumor effects of the combination (FIG. 19 , panelA). The effect of CD226 is specific, since the inhibition of othermembers of the TNF receptor superfamily (OX40L or 4-1BBL) or blockade ofthe B7 costimulatory molecule (CD28) using CTLA4-Ig preserved theanti-tumor effect mediated by the combination therapy (FIG. 19 , panelsB-D).

Requirement for CD226 in TIGIT Null Animals

Overall single-cell sorting RNA-seq and FACS phenotyping data showedthat anti-PD-1 favored the expression of CD226, while anti-GITRtreatment down-regulated surface expression of TIGIT, synergisticallyrestoring the homeostatic T cell function.

We showed that the CD226 signaling pathway was required for enhancedtumor surveillance in TIGIT−/− mice (FIGS. 14, 15 ). Additionally, micebearing MC38 tumor cells overexpressing CD155/PVR6, which is the majorligand for CD226, showed significant delay of tumor growth uponanti-PD-1 or anti-GITR or combination therapy in comparison toMC38-empty vector (MC38-EV) tumor cells or mice treated with isotypecontrol (FIG. 20 ). Immune profiling analysis of mice transplanted withMC38-CD155 confirmed sustained higher CD155 expression level onMC38-CD155 cells over M38-EV (empty vector) post-implantation. We foundthat CD155 over-expression on MC38 tumor cells was associated withdecreased detectable CD226 expression on CD4+, CD8+ T and Tregs cells(FIG. 21A), while it boosted T cell activation as indicated by enhancedIFNγ (FIG. 21B) and 4-1 BB (FIG. 21C) expression on intra-tumoral Tcells. No effect was observed in the periphery.

Without being bound by any theory, it is hypothesized that CD226expression level should correlate with the overall T cell activationstrength and may be predictive of a better prognosis in cancer patients.Indeed, patients with high CD226 expression have significantly highersurvival probabilities in three types of cancer (skin cutaneousmelanoma, lung adenocarcinoma and sarcoma). These data support animmunotherapy strategy that boosts CD226 signaling while simultaneouslyblocking TIGIT for maximum T cell activation.

The forgoing experiments demonstrate the synergistic effect ofadministering an anti-GITR antibody in combination with an anti-PD1antibody. In particular, among other things, the experiments abovedemonstrate that the combined administration of an anti-GITR antibodyand anti-PD1 antibody induces tumor regression, provides long-term tumorremission, and induces tumor/antigen-specific immunologic memoryresponse.

Example 10: TCR Analysis

For TCR analysis, we developed a new bioinformatic pipeline rpsTCR forreconstructing and extracting TCR sequences, especially TCR-CDR3sequences from random priming short RNA sequencing reads. The rpsTCRtook paired- and single-end short reads and maps these reads to mouse orhuman genomes and transcriptomes, but not TCR gene loci and transcriptsusing TopHat (Bioinformatics 25, 1105-1111 (2009)) with defaultparameters. Mapped reads were discarded and unmapped reads are recycledfor extraction of TCR sequences. Low quality nucleotides in the unmappedreads were trimmed. Then reads with length less than 35 bp were filteredout using HTQC toolkit (Bioinformatics 14, 33 (2013). QC passed shortreads was assembled into longer reads using iSSAKE (Bioinformatics 25,458-464 (2009)) default setting. TCRklass (J Immunol 194, 446-454(2015)) was used to identify CDR3 sequences with Scr (conserved residuesupport score) set from default 1.7 to 2. A targeted TCR-seq data from ahealthy human PBMC samples was used as a positive control to evaluatewhether the extra steps introduced to the pipeline resulted in higherfalse positive or false negative rates comparing to TCRklass alone.

The majority of unique CDR3 sequences from TCRB (64,031) or TCRA(51,448) were detected by both rpsTCR and TCRklass. The squaredcorrelations between rpsTCR and TCRklass were 0.9999 and 0.9365 forTCRB-CDR3 and TCRA-CDR3, respectively. Six TCR-negative cancer ornon-cancer cell lines were used as negative controls. No CDR3 sequenceswere detected by rpsTCR, whereas some CDR sequences were extracted byTCRklass from some TCR-negative cancer cell lines.

To further validate the performance of the subject pipeline, wesequenced a heathy mouse PBMC sample using both targeted TCR-seq andrandom priming RNA-seq approaches (200M, 2×100 bp). Although the numberof CDR3 sequences assembled from RNA-seq data was much smaller than thatfrom the targeted TCR-seq approach, about 45% of the CDR3 sequencesidentified from RNA-seq data using rpsTCR were also observed among CDR3sequences from targeted TCR-seq. Because of the technique limitation oftargeted TCR-seq, it is not surprising that a fraction of the CDR3sequences we extracted from RNA-seq data were not present in the TCR-seqresults. For example, the efficiency of 5′ race adapter used fortargeted TCR-seq is generally low and the multiply PCR tends to amplifyhigh frequency TCRs, thus only a small portion of TCRs can be targeted.As expected, much higher percentage (˜70%) of the CDR3 sequencesidentified from RNA-seq data using rpsTCR were also observed among highfrequency CDR3 sequences (>=0.1%) from targeted TCR-seq, while onlyabout 40% extracted using TCRklass alone. Moreover, we cut the 100 bpread length in 50 bp segments and randomly selected 200M reads. Amongthe top 10 CDR3 sequences ranked by targeted TCR-seq approach, 8 CDR3sequences were detected by our rpsTCR, while only 3 were detected byTCRklass. We then applied our rpsTCR pipeline to extracting CDR3sequences from the single cell RNA-seq data generated from intratumoralCD8 T cells of MC38 treated with different antibodies. Our CDR3_beta andCDR3_alpha sequence detection rates were comparable to published datausing targeted TCR-seq approach to detect TCR sequences from single cellsequencing of T cells

The present invention is not to be limited in scope by the specificembodiments described herein. Indeed, various modifications of theinvention in addition to those described herein will become apparent tothose skilled in the art from the foregoing description and theaccompanying figures. Such modifications are intended to fall within thescope of the appended claims.

What is claimed is: 1.-13. (canceled)
 14. An isolated antibody orantigen-binding fragment thereof that binds glucocorticoid-induced tumornecrosis factor receptor (GITR), wherein the antibody or antigen-bindingfragment comprises: (a) the complementarity determining regions (CDRs)of a heavy chain variable region (HCVR) having an amino acid sequence asset forth in Table 1; and (b) the CDRs of a light chain variable region(LCVR) having an amino acid sequence as set forth in Table
 1. 15. Theisolated antibody or antigen-binding fragment of claim 14, wherein theantibody or antigen-binding fragment comprises an HCVR having an aminoacid sequence as set forth in Table 1 and a LCVR having an amino acidsequence as set forth in Table
 1. 16. The isolated antibody orantigen-binding fragment of claim 14, wherein the antibody orantigen-binding fragment comprises: (i) a HCDR1 domain having an aminoacid sequence selected from the group consisting of SEQ ID NOs: 100,164, 196, 244, 292, 340, and 348; (ii) a HCDR2 domain having an aminoacid sequence selected from the group consisting of SEQ ID NOs: 102,166, 198, 246, 294, 342, and 350; (iii) a HCDR3 domain having an aminoacid sequence selected from the group consisting of SEQ ID NOs: 104,168, 200, 248, 296, 344, 352; (iv) a LCDR1 domain having an amino acidsequence selected from the group consisting of SEQ ID NOs: 108, 172,204, 252, 300, and 404 (v) a LCDR2 domain having an amino acid sequenceselected from the group consisting of SEQ ID NOs: 110 (GAS), 174 (TAS),206 (AAS), 254 (AAS), 302 (AAS), and 406 (AAS), and (vi) a LCDR3 domainhaving an amino acid sequence selected from the group consisting of SEQID Nos: 112, 176, 208, 256, 304, and
 408. 17. The isolated antibody orantigen-binding fragment of claim 14, wherein the antibody orantigen-binding fragment comprises: (vii) a heavy chain complementaritydetermining region (HCDR)-1 comprising SEQ ID NO: 100; an HCDR2comprising SEQ ID NO: 102; an HCDR3 comprising SEQ ID NO: 104; a lightchain complementarity determining region (LCDR)-1 comprising SEQ ID NO:108; an LCDR2 comprising SEQ ID NO: 110 (GAS); and an LCDR3 comprisingSEQ ID NO: 112; (viii) a heavy chain complementarity determining region(HCDR)-1 comprising SEQ ID NO: 164; an HCDR2 comprising SEQ ID NO: 166;an HCDR3 comprising SEQ ID NO: 168; a light chain complementaritydetermining region (LCDR)-1 comprising SEQ ID NO: 172; an LCDR2comprising SEQ ID NO: 174 (TAS); and an LCDR3 comprising SEQ ID NO: 176;(ix) a heavy chain complementarity determining region (HCDR)-1comprising SEQ ID NO: 196; an HCDR2 comprising SEQ ID NO: 198; an HCDR3comprising SEQ ID NO: 200; a light chain complementarity determiningregion (LCDR)-1 comprising SEQ ID NO: 204; an LCDR2 comprising SEQ IDNO: 206 (AAS); and an LCDR3 comprising SEQ ID NO: 208; (x) a heavy chaincomplementarity determining region (HCDR)-1 comprising SEQ ID NO: 244;an HCDR2 comprising SEQ ID NO: 246; an HCDR3 comprising SEQ ID NO: 248;a light chain complementarity determining region (LCDR)-1 comprising SEQID NO: 252; an LCDR2 comprising SEQ ID NO: 254 (AAS); and an LCDR3comprising SEQ ID NO: 256; (xi) a heavy chain complementaritydetermining region (HCDR)-1 comprising SEQ ID NO: 292; an HCDR2comprising SEQ ID NO: 294; an HCDR3 comprising SEQ ID NO: 296; a lightchain complementarity determining region (LCDR)-1 comprising SEQ ID NO:300; an LCDR2 comprising SEQ ID NO: 302 (AAS); and an LCDR3 comprisingSEQ ID NO: 304; (xii) a heavy chain complementarity determining region(HCDR)-1 comprising SEQ ID NO: 340; an HCDR2 comprising SEQ ID NO: 342;an HCDR3 comprising SEQ ID NO: 344; a light chain complementaritydetermining region (LCDR)-1 comprising SEQ ID NO: 404; an LCDR2comprising SEQ ID NO: 406 (AAS); and an LCDR3 comprising SEQ ID NO: 408;or (xiii) a heavy chain complementarity determining region (HCDR)-1comprising SEQ ID NO: 348; an HCDR2 comprising SEQ ID NO: 350; an HCDR3comprising SEQ ID NO: 352; a light chain complementarity determiningregion (LCDR)-1 comprising SEQ ID NO: 404; an LCDR2 comprising SEQ IDNO: 406 (AAS); and an LCDR3 comprising SEQ ID NO:
 408. 18.-19.(canceled)
 20. A pharmaceutical composition comprising the antibody orantigen-binding fragment of claim 14 and a pharmaceutically acceptablecarrier or diluent.
 21. A method for treating cancer in a subjectcomprising administering to the subject the composition of claim
 20. 22.A method of modulating anti-tumor immune response in a subjectcomprising administering to the subject the antibody that binds GITR ofclaim 14 or antigen-binding fragment thereof.
 23. The method of claim22, further comprising administering to the subject an antibody orantigen-binding fragment thereof that binds to a second T-cellactivating receptor.
 24. The method of claim 23, wherein the T-cellactivating receptor is CD28, OX40, CD137, CD27, or HVEM.
 25. The methodof claim 22, further comprising administering to the subject an antibodyor antigen-binding fragment thereof that binds to a T-cell inhibitoryreceptor.
 26. The method of claim 25, wherein the T-cell inhibitoryreceptor is CTLA-4, PD-1, TIM-3, BTLA, VISTA, or LAG-3.
 27. The methodof claim 22, further comprising administering radiation therapy to saidsubject.
 28. The method of claim 22, further comprising administeringone or more chemotherapeutic agent.
 29. The method of claim 26, whereinthe T-cell inhibitory receptor is PD1.
 30. The method of claim 29,wherein the antibody that binds to a T-cell inhibitory receptor is REGN2810.
 31. The method of claim 22, wherein the antibody orantigen-binding fragment comprises: (i) a heavy chain complementaritydetermining region (HCDR)-1 comprising SEQ ID NO: 100; an HCDR2comprising SEQ ID NO: 102; an HCDR3 comprising SEQ ID NO: 104; a lightchain complementarity determining region (LCDR)-1 comprising SEQ ID NO:108; an LCDR2 comprising SEQ ID NO: 110 (GAS); and an LCDR3 comprisingSEQ ID NO: 112; (ii) a heavy chain complementarity determining region(HCDR)-1 comprising SEQ ID NO: 164; an HCDR2 comprising SEQ ID NO: 166;an HCDR3 comprising SEQ ID NO: 168; a light chain complementaritydetermining region (LCDR)-1 comprising SEQ ID NO: 172; an LCDR2comprising SEQ ID NO: 174 (TAS); and an LCDR3 comprising SEQ ID NO: 176;(iii) a heavy chain complementarity determining region (HCDR)-1comprising SEQ ID NO: 196; an HCDR2 comprising SEQ ID NO: 198; an HCDR3comprising SEQ ID NO: 200; a light chain complementarity determiningregion (LCDR)-1 comprising SEQ ID NO: 204; an LCDR2 comprising SEQ IDNO: 206 (AAS); and an LCDR3 comprising SEQ ID NO: 208; (iv) a heavychain complementarity determining region (HCDR)-1 comprising SEQ ID NO:244; an HCDR2 comprising SEQ ID NO: 246; an HCDR3 comprising SEQ ID NO:248; a light chain complementarity determining region (LCDR)-1comprising SEQ ID NO: 252; an LCDR2 comprising SEQ ID NO: 254 (AAS); andan LCDR3 comprising SEQ ID NO: 256; (v) a heavy chain complementaritydetermining region (HCDR)-1 comprising SEQ ID NO: 292; an HCDR2comprising SEQ ID NO: 294; an HCDR3 comprising SEQ ID NO: 296; a lightchain complementarity determining region (LCDR)-1 comprising SEQ ID NO:300; an LCDR2 comprising SEQ ID NO: 302 (AAS); and an LCDR3 comprisingSEQ ID NO: 304; (vi) a heavy chain complementarity determining region(HCDR)-1 comprising SEQ ID NO: 340; an HCDR2 comprising SEQ ID NO: 342;an HCDR3 comprising SEQ ID NO: 344; a light chain complementaritydetermining region (LCDR)-1 comprising SEQ ID NO: 404; an LCDR2comprising SEQ ID NO: 406 (AAS); and an LCDR3 comprising SEQ ID NO: 408;or a heavy chain complementarity determining region (HCDR)-1 comprisingSEQ ID NO: 348; an HCDR2 comprising SEQ ID NO: 350; an HCDR3 comprisingSEQ ID NO: 352; a light chain complementarity determining region(LCDR)-1 comprising SEQ ID NO: 404; an LCDR2 comprising SEQ ID NO: 406(AAS); and an LCDR3 comprising SEQ ID NO: 408.